31885220721 has 4 divisors (see below), whose sum is σ = 42513627632. Its totient is φ = 21256813812.

The previous prime is 31885220693. The next prime is 31885220729. The reversal of 31885220721 is 12702258813.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 31885220721 - 2⁹ = 31885220209 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 31885220721.

It is not an unprimeable number, because it can be changed into a prime (31885220729) 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 in 3 ways as a sum of consecutive naturals, for example, 5314203451 + ... + 5314203456.

It is an arithmetic number, because the mean of its divisors is an integer number (10628406908).

Almost surely, 2^31885220721 is an apocalyptic number.

It is an amenable number.

31885220721 is a deficient number, since it is larger than the sum of its proper divisors (10628406911).

31885220721 is a wasteful number, since it uses less digits than its factorization.

31885220721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10628406910.

The product of its (nonzero) digits is 53760, while the sum is 39.

The spelling of 31885220721 in words is "thirty-one billion, eight hundred eighty-five million, two hundred twenty thousand, seven hundred twenty-one".