21138880 has 56 divisors (see below), whose sum is σ = 57534048. Its totient is φ = 7246848.

The previous prime is 21138853. The next prime is 21138881. The reversal of 21138880 is 8883112.

It is a tau number, because it is divible by the number of its divisors (56).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138881) 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, 2479 + ... + 6958.

Almost surely, 2^21138880 is an apocalyptic number.

21138880 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21138880 is an abundant number, since it is smaller than the sum of its proper divisors (36395168).

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

21138880 is an equidigital number, since it uses as much as digits as its factorization.

21138880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9461 (or 9451 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 31.

The square root of 21138880 is about 4597.7037747119. The cubic root of 21138880 is about 276.4992713297.

The spelling of 21138880 in words is "twenty-one million, one hundred thirty-eight thousand, eight hundred eighty".