131309991 has 40 divisors (see below), whose sum is σ = 203076720. Its totient is φ = 84509568.

The previous prime is 131309957. The next prime is 131309993. The reversal of 131309991 is 199903131.

It is not a de Polignac number, because 131309991 - 2⁷ = 131309863 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (131309993) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 313180 + ... + 313598.

It is an arithmetic number, because the mean of its divisors is an integer number (5076918).

Almost surely, 2^131309991 is an apocalyptic number.

131309991 is a deficient number, since it is larger than the sum of its proper divisors (71766729).

131309991 is an equidigital number, since it uses as much as digits as its factorization.

131309991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 557 (or 548 counting only the distinct ones).

The product of its (nonzero) digits is 6561, while the sum is 36.

The square root of 131309991 is about 11459.0571601681. The cubic root of 131309991 is about 508.2755947201.

The spelling of 131309991 in words is "one hundred thirty-one million, three hundred nine thousand, nine hundred ninety-one".