31721723881 has 2 divisors, whose sum is σ = 31721723882. Its totient is φ = 31721723880.

The previous prime is 31721723867. The next prime is 31721723897. The reversal of 31721723881 is 18832712713.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 30383627481 + 1338096400 = 174309^2 + 36580^2 .

It is a cyclic number.

It is not a de Polignac number, because 31721723881 - 2⁵ = 31721723849 is a prime.

It is a super-2 number, since 2×31721723881² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (31721723381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15860861940 + 15860861941.

It is an arithmetic number, because the mean of its divisors is an integer number (15860861941).

Almost surely, 2^31721723881 is an apocalyptic number.

It is an amenable number.

31721723881 is a deficient number, since it is larger than the sum of its proper divisors (1).

31721723881 is an equidigital number, since it uses as much as digits as its factorization.

31721723881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 112896, while the sum is 43.

The spelling of 31721723881 in words is "thirty-one billion, seven hundred twenty-one million, seven hundred twenty-three thousand, eight hundred eighty-one".