129631991 has 2 divisors, whose sum is σ = 129631992. Its totient is φ = 129631990.

The previous prime is 129631981. The next prime is 129631993. The reversal of 129631991 is 199136921.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-129631991 is a prime.

Together with 129631993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (129631993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64815995 + 64815996.

It is an arithmetic number, because the mean of its divisors is an integer number (64815996).

Almost surely, 2^129631991 is an apocalyptic number.

129631991 is a deficient number, since it is larger than the sum of its proper divisors (1).

129631991 is an equidigital number, since it uses as much as digits as its factorization.

129631991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 26244, while the sum is 41.

The square root of 129631991 is about 11385.6045513622. The cubic root of 129631991 is about 506.1012350369.

The spelling of 129631991 in words is "one hundred twenty-nine million, six hundred thirty-one thousand, nine hundred ninety-one".