21705900 has 36 divisors (see below), whose sum is σ = 62803272. Its totient is φ = 5788160.

The previous prime is 21705899. The next prime is 21705947. The reversal of 21705900 is 950712.

It is a super-2 number, since 2×21705900² = 942292189620000, which contains 22 as substring.

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, 35877 + ... + 36476.

Almost surely, 2^21705900 is an apocalyptic number.

21705900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21705900 is an abundant number, since it is smaller than the sum of its proper divisors (41097372).

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

21705900 is a wasteful number, since it uses less digits than its factorization.

21705900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72370 (or 72363 counting only the distinct ones).

The product of its (nonzero) digits is 630, while the sum is 24.

The square root of 21705900 is about 4658.9591112179. The cubic root of 21705900 is about 278.9497218016.

The spelling of 21705900 in words is "twenty-one million, seven hundred five thousand, nine hundred".