Four thousand (4000) is the natural number following 3999 and preceding 4001. It is a decagonal number.

Cardinal	Four thousand
Ordinal	Four thousandth
Factorization
Binary	111110100000
Hexadecimal	FA0

Selected numbers in the range 4001-4999

4005 - triangular number

4007 - safe prime

4010 - magic constant of n×n magic square and n-Queens Problem for n = 20.

4011 - PLU code for yellow bananas

4019 - Sophie Germain prime

4028 - sum of the first 45 primes

4030 - 3rd weird number

4031 - sum of the cubes of the first six primes

4033 - 6th super-Poulet number

4060 - tetrahedral number

4073 - Sophie Germain prime

4079 - safe prime

4095 - triangular number

4096 - 12th power of two, 16th cube, 64^2

4104 = 2^3 + 16^3 = 9^3 + 15^3

4127 - safe prime

4139 - safe prime

4166 - centered heptagonal number

4181 - Fibonacci number

4186 - triangular number

4200 - nonagonal number, pentagonal pyramidal number

4210 - 11th semi-meandric number

4211 - Sophie Germain prime

4219 - cuban prime of the form x = y + 1

4225 = 65^2, centered octagonal number

4227 - sum of the first 46 primes

4257 - decagonal number

4259 - safe prime

4271 - Sophie Germain prime

4278 - triangular number

4283 - safe prime

4324 - 23rd square pyramidal number

4349 - Sophie Germain prime

4356 - sum of the cubes of the first eleven integers, 66^2

4369 - 7th super-Poulet number

4371 - triangular number

4373 - Sophie Germain prime

4391 - Sophie Germain prime

4400 - the number of missing persons in the sci-fi show The 4400

4409 - Sophie Germain prime

4411 - centered heptagonal number

4438 - sum of the first 47 primes

4446 - nonagonal number

4447 - cuban prime of the form x = y + 1

4465 - triangular number

4481 - Sophie Germain prime

4489 = 67^2, centered octagonal number

4495 - tetrahedral number

4503 - largest number not the sum of four or fewer squares of composites

4505 - 5th Zeisel number

4522 - decagonal number

4547 - safe prime

4560 - triangular number

4579 - octahedral number

4607 - Woodall number

4624 = 68^2

4641 - magic constant of n×n magic square and n-Queens Problem for n = 21.

4656 - triangular number

4661 - sum of the first 48 primes

4663 - centered heptagonal number

4679 - safe prime

4681 - 8th super-Poulet number

4699 - nonagonal number

4703 - safe prime

4705 = 48² + 49² = 17² + 18² + ... 26²

4727 - sum of the squares of the first twelve primes

4733 - Sophie Germain prime

4753 - triangular number

4761 = 69^2, centered octagonal number

4787 - safe prime

4788 - 14th Keith number

4793 - Sophie Germain prime

4795 - decagonal number

4799 - safe prime

4801 - cuban prime of the form x = y + 2

4851 - triangular number, pentagonal pyramidal number

4871 - Sophie Germain prime

4879 - 11th Kaprekar number

4888 - sum of the first 49 primes

4900 - the only square-pyramidal square other than 1[1], 70^2

4913 - 17th cube

4919 - Sophie Germain prime, safe prime

4922 - centered heptagonal number

4941 - centered cube number

4943 - Sophie Germain prime

4950 - triangular number, 12th Kaprekar number

4959 - nonagonal number

4960 - tetrahedral number; greater of 4th pair of Smith brothers