21290820 has 24 divisors (see below), whose sum is σ = 59614464. Its totient is φ = 5677536.

The previous prime is 21290813. The next prime is 21290839. The reversal of 21290820 is 2809212.

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, 177364 + ... + 177483.

It is an arithmetic number, because the mean of its divisors is an integer number (2483936).

Almost surely, 2^21290820 is an apocalyptic number.

21290820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21290820 is an abundant number, since it is smaller than the sum of its proper divisors (38323644).

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

21290820 is a wasteful number, since it uses less digits than its factorization.

21290820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 354859 (or 354857 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 21290820 is about 4614.1976550642. The cubic root of 21290820 is about 277.1601553561.

The spelling of 21290820 in words is "twenty-one million, two hundred ninety thousand, eight hundred twenty".