21621055680 has 448 divisors, whose sum is σ = 87489792000. Its totient is φ = 4923887616.

The previous prime is 21621055669. The next prime is 21621055693. The reversal of 21621055680 is 8655012612.

21621055680 is a `hidden beast` number, since 2 + 1 + 6 + 21 + 0 + 556 + 80 = 666.

It is a Cunningham number, because it is equal to 147041²-1.

It is a tau number, because it is divible by the number of its divisors (448).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 23526261 + ... + 23527179.

Almost surely, 2^21621055680 is an apocalyptic number.

21621055680 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 21621055680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43744896000).

21621055680 is an abundant number, since it is smaller than the sum of its proper divisors (65868736320).

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

21621055680 is a wasteful number, since it uses less digits than its factorization.

21621055680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1341 (or 1325 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 36.

The spelling of 21621055680 in words is "twenty-one billion, six hundred twenty-one million, fifty-five thousand, six hundred eighty".