21087556 has 12 divisors (see below), whose sum is σ = 42175168. Its totient is φ = 9037512.

The previous prime is 21087529. The next prime is 21087557. The reversal of 21087556 is 65578012.

21087556 is an admirable number.

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21087557) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 376536 + ... + 376591.

Almost surely, 2^21087556 is an apocalyptic number.

It is an amenable number.

21087556 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21087556 is a wasteful number, since it uses less digits than its factorization.

21087556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 753138 (or 753136 counting only the distinct ones).

The product of its (nonzero) digits is 16800, while the sum is 34.

The square root of 21087556 is about 4592.1189008997. The cubic root of 21087556 is about 276.2753151388.

The spelling of 21087556 in words is "twenty-one million, eighty-seven thousand, five hundred fifty-six".