21721963937520 has 1440 divisors, whose sum is σ = 91416135492864. Its totient is φ = 4236465192960.

The previous prime is 21721963937497. The next prime is 21721963937551. The reversal of 21721963937520 is 2573936912712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 287 ways as a sum of consecutive naturals, for example, 10716310747 + ... + 10716312773.

Almost surely, 2^{21721963937520} is an apocalyptic number.

21721963937520 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 21721963937520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45708067746432).

21721963937520 is an abundant number, since it is smaller than the sum of its proper divisors (69694171555344).

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

21721963937520 is a wasteful number, since it uses less digits than its factorization.

21721963937520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2539 (or 2515 counting only the distinct ones).

The product of its (nonzero) digits is 8573040, while the sum is 57.

The spelling of 21721963937520 in words is "twenty-one trillion, seven hundred twenty-one billion, nine hundred sixty-three million, nine hundred thirty-seven thousand, five hundred twenty".