31517521491 has 4 divisors (see below), whose sum is σ = 42023361992. Its totient is φ = 21011680992.

The previous prime is 31517521459. The next prime is 31517521507. The reversal of 31517521491 is 19412571513.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 31517521491 - 2⁵ = 31517521459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31517521991) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5252920246 + ... + 5252920251.

It is an arithmetic number, because the mean of its divisors is an integer number (10505840498).

Almost surely, 2^31517521491 is an apocalyptic number.

31517521491 is a deficient number, since it is larger than the sum of its proper divisors (10505840501).

31517521491 is a wasteful number, since it uses less digits than its factorization.

31517521491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10505840500.

The product of its digits is 37800, while the sum is 39.

The spelling of 31517521491 in words is "thirty-one billion, five hundred seventeen million, five hundred twenty-one thousand, four hundred ninety-one".