21807280 has 40 divisors (see below), whose sum is σ = 55313424. Its totient is φ = 7929600.

The previous prime is 21807271. The next prime is 21807283. The reversal of 21807280 is 8270812.

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21807283) 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, 11511 + ... + 13270.

It is the magic constant of a 352 × 352 magic square.

Almost surely, 2^21807280 is an apocalyptic number.

21807280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21807280 is an abundant number, since it is smaller than the sum of its proper divisors (33506144).

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

21807280 is a wasteful number, since it uses less digits than its factorization.

21807280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24805 (or 24799 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 28.

The square root of 21807280 is about 4669.8265492414. The cubic root of 21807280 is about 279.3833367547.

The spelling of 21807280 in words is "twenty-one million, eight hundred seven thousand, two hundred eighty".