21637120 has 48 divisors (see below), whose sum is σ = 51940980. Its totient is φ = 8650752.

The previous prime is 21637097. The next prime is 21637123. The reversal of 21637120 is 2173612.

It can be written as a sum of positive squares in 2 ways, for example, as 17572864 + 4064256 = 4192^2 + 2016^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21637091 and 21637100.

It is not an unprimeable number, because it can be changed into a prime (21637123) 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, 9184 + ... + 11296.

Almost surely, 2^21637120 is an apocalyptic number.

21637120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21637120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25970490).

21637120 is an abundant number, since it is smaller than the sum of its proper divisors (30303860).

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

21637120 is an equidigital number, since it uses as much as digits as its factorization.

21637120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2140 (or 2120 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21637120 is about 4651.5717773673. The cubic root of 21637120 is about 278.6547718444.

The spelling of 21637120 in words is "twenty-one million, six hundred thirty-seven thousand, one hundred twenty".