21455920 has 20 divisors (see below), whose sum is σ = 49885200. Its totient is φ = 8582336.

The previous prime is 21455891. The next prime is 21455927. The reversal of 21455920 is 2955412.

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (21455927) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134020 + ... + 134179.

It is an arithmetic number, because the mean of its divisors is an integer number (2494260).

Almost surely, 2^21455920 is an apocalyptic number.

21455920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21455920 is an abundant number, since it is smaller than the sum of its proper divisors (28429280).

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

21455920 is a wasteful number, since it uses less digits than its factorization.

21455920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268212 (or 268206 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 28.

The square root of 21455920 is about 4632.0535402778. The cubic root of 21455920 is about 277.8747257452.

The spelling of 21455920 in words is "twenty-one million, four hundred fifty-five thousand, nine hundred twenty".