21537986400 has 576 divisors, whose sum is σ = 89629263360. Its totient is φ = 4889548800.

The previous prime is 21537986377. The next prime is 21537986413. The reversal of 21537986400 is 468973512.

21537986400 is a `hidden beast` number, since 2 + 153 + 7 + 98 + 6 + 400 = 666.

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 95 ways as a sum of consecutive naturals, for example, 27366807 + ... + 27367593.

It is an arithmetic number, because the mean of its divisors is an integer number (155606360).

It is a 1-persistent number, because it is pandigital, but 2⋅21537986400 = 43075972800 is not.

Almost surely, 2^21537986400 is an apocalyptic number.

21537986400 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 21537986400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44814631680).

21537986400 is an abundant number, since it is smaller than the sum of its proper divisors (68091276960).

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

21537986400 is a wasteful number, since it uses less digits than its factorization.

21537986400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1004 (or 985 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 45.

The spelling of 21537986400 in words is "twenty-one billion, five hundred thirty-seven million, nine hundred eighty-six thousand, four hundred".