21087936 has 84 divisors (see below), whose sum is σ = 62447424. Its totient is φ = 6796800.

The previous prime is 21087919. The next prime is 21087943. The reversal of 21087936 is 63978012.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21087936.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17266 + ... + 18446.

Almost surely, 2^21087936 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21087936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31223712).

21087936 is an abundant number, since it is smaller than the sum of its proper divisors (41359488).

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

21087936 is a wasteful number, since it uses less digits than its factorization.

21087936 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1230 (or 1217 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21087936 is about 4592.1602759486. The cubic root of 21087936 is about 276.2769746323.

The spelling of 21087936 in words is "twenty-one million, eighty-seven thousand, nine hundred thirty-six".