21139920 has 80 divisors (see below), whose sum is σ = 72822720. Its totient is φ = 5636736.

The previous prime is 21139919. The next prime is 21139931. The reversal of 21139920 is 2993112.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2734 + ... + 7053.

It is an arithmetic number, because the mean of its divisors is an integer number (910284).

Almost surely, 2^21139920 is an apocalyptic number.

21139920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21139920 is an abundant number, since it is smaller than the sum of its proper divisors (51682800).

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

21139920 is a wasteful number, since it uses less digits than its factorization.

21139920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9809 (or 9797 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 21139920 is about 4597.8168732563. The cubic root of 21139920 is about 276.5038057000.

The spelling of 21139920 in words is "twenty-one million, one hundred thirty-nine thousand, nine hundred twenty".