21515008 has 36 divisors (see below), whose sum is σ = 43251040. Its totient is φ = 10681344.

The previous prime is 21515003. The next prime is 21515009. The reversal of 21515008 is 80051512.

It is a self number, because there is not a number n which added to its sum of digits gives 21515008.

It is not an unprimeable number, because it can be changed into a prime (21515003) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 58441 + ... + 58807.

Almost surely, 2^21515008 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 21515008, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21625520).

21515008 is an abundant number, since it is smaller than the sum of its proper divisors (21736032).

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

21515008 is an equidigital number, since it uses as much as digits as its factorization.

21515008 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 612 (or 598 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 22.

The square root of 21515008 is about 4638.4273196850. The cubic root of 21515008 is about 278.1295740190.

The spelling of 21515008 in words is "twenty-one million, five hundred fifteen thousand, eight".