21906920 has 48 divisors (see below), whose sum is σ = 57343140. Its totient is φ = 7510272.

The previous prime is 21906917. The next prime is 21906949. The reversal of 21906920 is 2960912.

It can be written as a sum of positive squares in 2 ways, for example, as 21473956 + 432964 = 4634^2 + 658^2 .

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, 3629 + ... + 7548.

Almost surely, 2^21906920 is an apocalyptic number.

21906920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21906920 is an abundant number, since it is smaller than the sum of its proper divisors (35436220).

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

21906920 is a wasteful number, since it uses less digits than its factorization.

21906920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11202 (or 11191 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 21906920 is about 4680.4828810711. The cubic root of 21906920 is about 279.8082019830.

The spelling of 21906920 in words is "twenty-one million, nine hundred six thousand, nine hundred twenty".