21057020 has 12 divisors (see below), whose sum is σ = 44219784. Its totient is φ = 8422800.

The previous prime is 21057019. The next prime is 21057053. The reversal of 21057020 is 2075012.

It is a self number, because there is not a number n which added to its sum of digits gives 21057020.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 526406 + ... + 526445.

It is an arithmetic number, because the mean of its divisors is an integer number (3684982).

Almost surely, 2^21057020 is an apocalyptic number.

21057020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21057020 is an abundant number, since it is smaller than the sum of its proper divisors (23162764).

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

21057020 is a wasteful number, since it uses less digits than its factorization.

21057020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1052860 (or 1052858 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 21057020 is about 4588.7928695900. The cubic root of 21057020 is about 276.1418965102.

The spelling of 21057020 in words is "twenty-one million, fifty-seven thousand, twenty".