21537809280 has 896 divisors, whose sum is σ = 85969084320. Its totient is φ = 5123948544.

The previous prime is 21537809243. The next prime is 21537809299. The reversal of 21537809280 is 8290873512.

It is a happy number.

21537809280 is a `hidden beast` number, since 21 + 537 + 8 + 0 + 92 + 8 + 0 = 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 111 ways as a sum of consecutive naturals, for example, 321459807 + ... + 321459873.

Almost surely, 2^21537809280 is an apocalyptic number.

21537809280 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 21537809280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42984542160).

21537809280 is an abundant number, since it is smaller than the sum of its proper divisors (64431275040).

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

21537809280 is an equidigital number, since it uses as much as digits as its factorization.

21537809280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170 (or 143 counting only the distinct ones).

The product of its (nonzero) digits is 241920, while the sum is 45.

The spelling of 21537809280 in words is "twenty-one billion, five hundred thirty-seven million, eight hundred nine thousand, two hundred eighty".