21065880 has 64 divisors (see below), whose sum is σ = 68947200. Its totient is φ = 5106560.

The previous prime is 21065843. The next prime is 21065887. The reversal of 21065880 is 8856012.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065887) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6660 + ... + 9299.

It is an arithmetic number, because the mean of its divisors is an integer number (1077300).

Almost surely, 2^21065880 is an apocalyptic number.

21065880 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21065880 is an abundant number, since it is smaller than the sum of its proper divisors (47881320).

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

21065880 is a wasteful number, since it uses less digits than its factorization.

21065880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15984 (or 15980 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 30.

The square root of 21065880 is about 4589.7581635637. The cubic root of 21065880 is about 276.1806211118.

It can be divided in two parts, 21065 and 880, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21065880 in words is "twenty-one million, sixty-five thousand, eight hundred eighty".