131001991 has 2 divisors, whose sum is σ = 131001992. Its totient is φ = 131001990.

The previous prime is 131001989. The next prime is 131002009. The reversal of 131001991 is 199100131.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 131001991 - 2¹ = 131001989 is a prime.

Together with 131001989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (131001901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65500995 + 65500996.

It is an arithmetic number, because the mean of its divisors is an integer number (65500996).

Almost surely, 2^131001991 is an apocalyptic number.

131001991 is a deficient number, since it is larger than the sum of its proper divisors (1).

131001991 is an equidigital number, since it uses as much as digits as its factorization.

131001991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 243, while the sum is 25.

The square root of 131001991 is about 11445.6101191680. The cubic root of 131001991 is about 507.8778807767.

The spelling of 131001991 in words is "one hundred thirty-one million, one thousand, nine hundred ninety-one".