21684920 has 16 divisors (see below), whose sum is σ = 48791160. Its totient is φ = 8673952.

The previous prime is 21684917. The next prime is 21684931. The reversal of 21684920 is 2948612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 271022 + ... + 271101.

Almost surely, 2^21684920 is an apocalyptic number.

21684920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21684920 is an abundant number, since it is smaller than the sum of its proper divisors (27106240).

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

21684920 is a wasteful number, since it uses less digits than its factorization.

21684920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 542134 (or 542130 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21684920 is about 4656.7069909970. The cubic root of 21684920 is about 278.8598191833.

The spelling of 21684920 in words is "twenty-one million, six hundred eighty-four thousand, nine hundred twenty".