21087920 has 40 divisors (see below), whose sum is σ = 56035104. Its totient is φ = 7229952.

The previous prime is 21087919. The next prime is 21087943. The reversal of 21087920 is 2978012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18269 + ... + 19388.

Almost surely, 2^21087920 is an apocalyptic number.

21087920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21087920 is an abundant number, since it is smaller than the sum of its proper divisors (34947184).

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

21087920 is a wasteful number, since it uses less digits than its factorization.

21087920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37677 (or 37671 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 21087920 is about 4592.1585338488. The cubic root of 21087920 is about 276.2769047593.

The spelling of 21087920 in words is "twenty-one million, eighty-seven thousand, nine hundred twenty".