21257381280 has 96 divisors (see below), whose sum is σ = 67335105600. Its totient is φ = 5636943872.

The previous prime is 21257381273. The next prime is 21257381291. The reversal of 21257381280 is 8218375212.

It is a tau number, because it is divible by the number of its divisors (96).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37785 + ... + 209624.

It is an arithmetic number, because the mean of its divisors is an integer number (701407350).

Almost surely, 2^21257381280 is an apocalyptic number.

21257381280 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 21257381280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33667552800).

21257381280 is an abundant number, since it is smaller than the sum of its proper divisors (46077724320).

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

21257381280 is a wasteful number, since it uses less digits than its factorization.

21257381280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247606 (or 247598 counting only the distinct ones).

The product of its (nonzero) digits is 53760, while the sum is 39.

The spelling of 21257381280 in words is "twenty-one billion, two hundred fifty-seven million, three hundred eighty-one thousand, two hundred eighty".