21631680 has 336 divisors, whose sum is σ = 90342720. Its totient is φ = 4644864.

The previous prime is 21631663. The next prime is 21631691. The reversal of 21631680 is 8613612.

21631680 is a `hidden beast` number, since 21 + 631 + 6 + 8 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (336).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 584622 + ... + 584658.

Almost surely, 2^21631680 is an apocalyptic number.

21631680 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 21631680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45171360).

21631680 is an abundant number, since it is smaller than the sum of its proper divisors (68711040).

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

21631680 is a wasteful number, since it uses less digits than its factorization.

21631680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96 (or 83 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21631680 is about 4650.9869920265. The cubic root of 21631680 is about 278.6314167796.

The spelling of 21631680 in words is "twenty-one million, six hundred thirty-one thousand, six hundred eighty".