21288980 has 24 divisors (see below), whose sum is σ = 44823240. Its totient is φ = 8493440.

The previous prime is 21288973. The next prime is 21288983. The reversal of 21288980 is 8988212.

It can be written as a sum of positive squares in 4 ways, for example, as 3429904 + 17859076 = 1852^2 + 4226^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21288983) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8066 + ... + 10374.

It is an arithmetic number, because the mean of its divisors is an integer number (1867635).

Almost surely, 2^21288980 is an apocalyptic number.

21288980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21288980 is an abundant number, since it is smaller than the sum of its proper divisors (23534260).

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

21288980 is a wasteful number, since it uses less digits than its factorization.

21288980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2779 (or 2777 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 38.

The square root of 21288980 is about 4613.9982661462. The cubic root of 21288980 is about 277.1521708605.

The spelling of 21288980 in words is "twenty-one million, two hundred eighty-eight thousand, nine hundred eighty".