31991257321 has 9 divisors (see below), whose sum is σ = 32143833661. Its totient is φ = 31839404332.

The previous prime is 31991257289. The next prime is 31991257367. The reversal of 31991257321 is 12375219913.

The square root of 31991257321 is 178861.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 31991257321 - 2⁵ = 31991257289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31991257121) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 68503530 + ... + 68503996.

Almost surely, 2^31991257321 is an apocalyptic number.

31991257321 is the 178861-st square number.

31991257321 is the 89431-st centered octagonal number.

It is an amenable number.

31991257321 is a deficient number, since it is larger than the sum of its proper divisors (152576340).

31991257321 is an frugal number, since it uses more digits than its factorization.

31991257321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1700 (or 850 counting only the distinct ones).

The product of its digits is 102060, while the sum is 43.

The spelling of 31991257321 in words is "thirty-one billion, nine hundred ninety-one million, two hundred fifty-seven thousand, three hundred twenty-one".