21531656 has 48 divisors (see below), whose sum is σ = 43839600. Its totient is φ = 9909504.

The previous prime is 21531649. The next prime is 21531667. The reversal of 21531656 is 65613512.

It is a super-2 number, since 2×21531656² = 927224420204672, which contains 22 as substring.

Its product of digits (5400) is a multiple of the sum of its prime divisors (225).

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 11 ways as a sum of consecutive naturals, for example, 154835 + ... + 154973.

It is an arithmetic number, because the mean of its divisors is an integer number (913325).

Almost surely, 2^21531656 is an apocalyptic number.

It is an amenable number.

21531656 is an abundant number, since it is smaller than the sum of its proper divisors (22307944).

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

21531656 is a wasteful number, since it uses less digits than its factorization.

21531656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 246 (or 225 counting only the distinct ones).

The product of its digits is 5400, while the sum is 29.

The square root of 21531656 is about 4640.2215464350. The cubic root of 21531656 is about 278.2012930623.

The spelling of 21531656 in words is "twenty-one million, five hundred thirty-one thousand, six hundred fifty-six".