21680809920 has 1568 divisors, whose sum is σ = 103621856256. Its totient is φ = 4180377600.

The previous prime is 21680809901. The next prime is 21680809933. The reversal of 21680809920 is 2990808612.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 223 ways as a sum of consecutive naturals, for example, 305363485 + ... + 305363555.

Almost surely, 2^21680809920 is an apocalyptic number.

21680809920 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 21680809920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (51810928128).

21680809920 is an abundant number, since it is smaller than the sum of its proper divisors (81941046336).

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

21680809920 is a wasteful number, since it uses less digits than its factorization.

21680809920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141 (or 116 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 45.

The spelling of 21680809920 in words is "twenty-one billion, six hundred eighty million, eight hundred nine thousand, nine hundred twenty".