21537018720 has 240 divisors, whose sum is σ = 86866341408. Its totient is φ = 4922726400.

The previous prime is 21537018697. The next prime is 21537018721. The reversal of 21537018720 is 2781073512.

21537018720 is a `hidden beast` number, since 21 + 537 + 0 + 1 + 87 + 20 = 666.

It is a tau number, because it is divible by the number of its divisors (240).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21537018721) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 27981 + ... + 209420.

Almost surely, 2^21537018720 is an apocalyptic number.

21537018720 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 21537018720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43433170704).

21537018720 is an abundant number, since it is smaller than the sum of its proper divisors (65329322688).

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

21537018720 is a wasteful number, since it uses less digits than its factorization.

21537018720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 237435 (or 237418 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The spelling of 21537018720 in words is "twenty-one billion, five hundred thirty-seven million, eighteen thousand, seven hundred twenty".