31871921728 has 14 divisors (see below), whose sum is σ = 63245844806. Its totient is φ = 15935960832.

The previous prime is 31871921701. The next prime is 31871921743. The reversal of 31871921728 is 82712917813.

It can be written as a sum of positive squares in only one way, i.e., 30804462144 + 1067459584 = 175512^2 + 32672^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 248999325 + ... + 248999452.

Almost surely, 2^31871921728 is an apocalyptic number.

It is an amenable number.

31871921728 is a deficient number, since it is larger than the sum of its proper divisors (31373923078).

31871921728 is an equidigital number, since it uses as much as digits as its factorization.

31871921728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 497998789 (or 497998779 counting only the distinct ones).

The product of its digits is 338688, while the sum is 49.

The spelling of 31871921728 in words is "thirty-one billion, eight hundred seventy-one million, nine hundred twenty-one thousand, seven hundred twenty-eight".