21600640 has 32 divisors (see below), whose sum is σ = 51640560. Its totient is φ = 8640000.

The previous prime is 21600629. The next prime is 21600641. The reversal of 21600640 is 4600612.

It is a tau number, because it is divible by the number of its divisors (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21600641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16236 + ... + 17515.

Almost surely, 2^21600640 is an apocalyptic number.

21600640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21600640 is an abundant number, since it is smaller than the sum of its proper divisors (30039920).

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

21600640 is an equidigital number, since it uses as much as digits as its factorization.

21600640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33770 (or 33758 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21600640 is about 4647.6488679762. The cubic root of 21600640 is about 278.4980805608.

It can be divided in two parts, 21600 and 640, that multiplied together give a cube (13824000 = 240³).

The spelling of 21600640 in words is "twenty-one million, six hundred thousand, six hundred forty".