21656530 has 48 divisors (see below), whose sum is σ = 45780120. Its totient is φ = 7354368.

The previous prime is 21656513. The next prime is 21656539. The reversal of 21656530 is 3565612.

It can be written as a sum of positive squares in 4 ways, for example, as 19263321 + 2393209 = 4389^2 + 1547^2 .

It is not an unprimeable number, because it can be changed into a prime (21656539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 94456 + ... + 94684.

Almost surely, 2^21656530 is an apocalyptic number.

21656530 is an abundant number, since it is smaller than the sum of its proper divisors (24123590).

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

21656530 is a wasteful number, since it uses less digits than its factorization.

21656530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 443 (or 436 counting only the distinct ones).

The product of its (nonzero) digits is 5400, while the sum is 28.

The square root of 21656530 is about 4653.6577012067. The cubic root of 21656530 is about 278.7380711714.

The spelling of 21656530 in words is "twenty-one million, six hundred fifty-six thousand, five hundred thirty".