21512004 has 36 divisors (see below), whose sum is σ = 53329584. Its totient is φ = 6747776.

The previous prime is 21511999. The next prime is 21512017. The reversal of 21512004 is 40021512.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 367 + ... + 6569.

Almost surely, 2^21512004 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21512004, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26664792).

21512004 is an abundant number, since it is smaller than the sum of its proper divisors (31817580).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21512004 is a wasteful number, since it uses less digits than its factorization.

21512004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6244 (or 6225 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21512004 is about 4638.1034917302. The cubic root of 21512004 is about 278.1166289447.

Adding to 21512004 its reverse (40021512), we get a palindrome (61533516).

The spelling of 21512004 in words is "twenty-one million, five hundred twelve thousand, four".