21512640 has 56 divisors (see below), whose sum is σ = 68305680. Its totient is φ = 5736448.

The previous prime is 21512609. The next prime is 21512653. The reversal of 21512640 is 4621512.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 10245 + ... + 12164.

Almost surely, 2^21512640 is an apocalyptic number.

21512640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21512640 is an abundant number, since it is smaller than the sum of its proper divisors (46793040).

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

21512640 is a wasteful number, since it uses less digits than its factorization.

21512640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22429 (or 22419 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21512640 is about 4638.1720537298. The cubic root of 21512640 is about 278.1193697467.

The spelling of 21512640 in words is "twenty-one million, five hundred twelve thousand, six hundred forty".