21639120 has 40 divisors (see below), whose sum is σ = 67082016. Its totient is φ = 5770368.

The previous prime is 21639109. The next prime is 21639151. The reversal of 21639120 is 2193612.

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

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44842 + ... + 45321.

Almost surely, 2^21639120 is an apocalyptic number.

21639120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21639120 is an abundant number, since it is smaller than the sum of its proper divisors (45442896).

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

21639120 is a wasteful number, since it uses less digits than its factorization.

21639120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90179 (or 90173 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21639120 is about 4651.7867534959. The cubic root of 21639120 is about 278.6633572811.

The spelling of 21639120 in words is "twenty-one million, six hundred thirty-nine thousand, one hundred twenty".