21317620128 has 96 divisors (see below), whose sum is σ = 65258121600. Its totient is φ = 6090739200.

The previous prime is 21317620123. The next prime is 21317620139. The reversal of 21317620128 is 82102671312.

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

It is not an unprimeable number, because it can be changed into a prime (21317620123) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 290773 + ... + 356628.

It is an arithmetic number, because the mean of its divisors is an integer number (679772100).

Almost surely, 2^21317620128 is an apocalyptic number.

21317620128 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21317620128 is an abundant number, since it is smaller than the sum of its proper divisors (43940501472).

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

21317620128 is an equidigital number, since it uses as much as digits as its factorization.

21317620128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 647435 (or 647413 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 33.

The spelling of 21317620128 in words is "twenty-one billion, three hundred seventeen million, six hundred twenty thousand, one hundred twenty-eight".