31991257320 has 128 divisors (see below), whose sum is σ = 105086177280. Its totient is φ = 7726752000.

The previous prime is 31991257289. The next prime is 31991257367. The reversal of 31991257320 is 2375219913.

It is a Cunningham number, because it is equal to 178861²-1.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 313005 + ... + 402435.

It is an arithmetic number, because the mean of its divisors is an integer number (820985760).

Almost surely, 2^31991257320 is an apocalyptic number.

31991257320 is a gapful number since it is divisible by the number (30) 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 31991257320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (52543088640).

31991257320 is an abundant number, since it is smaller than the sum of its proper divisors (73094919960).

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

31991257320 is a wasteful number, since it uses less digits than its factorization.

31991257320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89727 (or 89723 counting only the distinct ones).

The product of its (nonzero) digits is 102060, while the sum is 42.

The spelling of 31991257320 in words is "thirty-one billion, nine hundred ninety-one million, two hundred fifty-seven thousand, three hundred twenty".