131997991 has 2 divisors, whose sum is σ = 131997992. Its totient is φ = 131997990.

The previous prime is 131997977. The next prime is 131998007. The reversal of 131997991 is 199799131.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-131997991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (131997191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65998995 + 65998996.

It is an arithmetic number, because the mean of its divisors is an integer number (65998996).

Almost surely, 2^131997991 is an apocalyptic number.

131997991 is a deficient number, since it is larger than the sum of its proper divisors (1).

131997991 is an equidigital number, since it uses as much as digits as its factorization.

131997991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 137781, while the sum is 49.

The square root of 131997991 is about 11489.0378622407. The cubic root of 131997991 is about 509.1617538439.

The spelling of 131997991 in words is "one hundred thirty-one million, nine hundred ninety-seven thousand, nine hundred ninety-one".