21255620 has 12 divisors (see below), whose sum is σ = 44636844. Its totient is φ = 8502240.

The previous prime is 21255613. The next prime is 21255653. The reversal of 21255620 is 2655212.

It can be written as a sum of positive squares in 2 ways, for example, as 5271616 + 15984004 = 2296^2 + 3998^2 .

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, 531371 + ... + 531410.

It is an arithmetic number, because the mean of its divisors is an integer number (3719737).

Almost surely, 2^21255620 is an apocalyptic number.

21255620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21255620 is an abundant number, since it is smaller than the sum of its proper divisors (23381224).

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

21255620 is a wasteful number, since it uses less digits than its factorization.

21255620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1062790 (or 1062788 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 21255620 is about 4610.3817629346. The cubic root of 21255620 is about 277.0073286301.

The spelling of 21255620 in words is "twenty-one million, two hundred fifty-five thousand, six hundred twenty".