21808260 has 36 divisors (see below), whose sum is σ = 66152268. Its totient is φ = 5815488.

The previous prime is 21808247. The next prime is 21808271. The reversal of 21808260 is 6280812.

It can be written as a sum of positive squares in 2 ways, for example, as 5308416 + 16499844 = 2304^2 + 4062^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 60399 + ... + 60758.

It is an arithmetic number, because the mean of its divisors is an integer number (1837563).

Almost surely, 2^21808260 is an apocalyptic number.

21808260 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21808260 is an abundant number, since it is smaller than the sum of its proper divisors (44344008).

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

21808260 is a wasteful number, since it uses less digits than its factorization.

21808260 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121172 (or 121167 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 21808260 is about 4669.9314770133. The cubic root of 21808260 is about 279.3875217726.

It can be divided in two parts, 2180 and 8260, that added together give a triangular number (10440 = T₁₄₄).

The spelling of 21808260 in words is "twenty-one million, eight hundred eight thousand, two hundred sixty".