21557656 has 16 divisors (see below), whose sum is σ = 41106600. Its totient is φ = 10595904.

The previous prime is 21557651. The next prime is 21557671. The reversal of 21557656 is 65675512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21557651) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 22365 + ... + 23308.

Almost surely, 2^21557656 is an apocalyptic number.

It is an amenable number.

21557656 is a deficient number, since it is larger than the sum of its proper divisors (19548944).

21557656 is a wasteful number, since it uses less digits than its factorization.

21557656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45738 (or 45734 counting only the distinct ones).

The product of its digits is 63000, while the sum is 37.

The square root of 21557656 is about 4643.0222915683. The cubic root of 21557656 is about 278.3132263036.

The spelling of 21557656 in words is "twenty-one million, five hundred fifty-seven thousand, six hundred fifty-six".