21639460 has 24 divisors (see below), whose sum is σ = 45957240. Its totient is φ = 8557824.

The previous prime is 21639437. The next prime is 21639469. The reversal of 21639460 is 6493612.

It can be written as a sum of positive squares in 4 ways, for example, as 350464 + 21288996 = 592^2 + 4614^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21639469) 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, 4299 + ... + 7858.

It is an arithmetic number, because the mean of its divisors is an integer number (1914885).

Almost surely, 2^21639460 is an apocalyptic number.

21639460 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21639460 is an abundant number, since it is smaller than the sum of its proper divisors (24317780).

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

21639460 is a wasteful number, since it uses less digits than its factorization.

21639460 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12255 (or 12253 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 21639460 is about 4651.8232984498. The cubic root of 21639460 is about 278.6648167527.

The spelling of 21639460 in words is "twenty-one million, six hundred thirty-nine thousand, four hundred sixty".