21157521280 has 64 divisors (see below), whose sum is σ = 57805382880. Its totient is φ = 7254005760.

The previous prime is 21157521251. The next prime is 21157521347. The reversal of 21157521280 is 8212575112.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-3 number, since 3×21157521280³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2356851 + ... + 2365810.

Almost surely, 2^21157521280 is an apocalyptic number.

21157521280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21157521280 is an abundant number, since it is smaller than the sum of its proper divisors (36647861600).

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

21157521280 is an equidigital number, since it uses as much as digits as its factorization.

21157521280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4722687 (or 4722675 counting only the distinct ones).

The product of its (nonzero) digits is 11200, while the sum is 34.

The spelling of 21157521280 in words is "twenty-one billion, one hundred fifty-seven million, five hundred twenty-one thousand, two hundred eighty".