21357017280 has 224 divisors, whose sum is σ = 76275468480. Its totient is φ = 5695017984.

The previous prime is 21357017243. The next prime is 21357017299. The reversal of 21357017280 is 8271075312.

21357017280 is a `hidden beast` number, since 2 + 1 + 3 + 570 + 1 + 7 + 2 + 80 = 666.

It is a super-2 number, since 2×21357017280² (a number of 21 digits) contains 22 as substring.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 684582 + ... + 715098.

Almost surely, 2^21357017280 is an apocalyptic number.

21357017280 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 21357017280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38137734240).

21357017280 is an abundant number, since it is smaller than the sum of its proper divisors (54918451200).

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

21357017280 is an frugal number, since it uses more digits than its factorization.

21357017280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30555 (or 30527 counting only the distinct ones).

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

The spelling of 21357017280 in words is "twenty-one billion, three hundred fifty-seven million, seventeen thousand, two hundred eighty".