231979991 has 2 divisors, whose sum is σ = 231979992. Its totient is φ = 231979990.

The previous prime is 231979967. The next prime is 231980027. The reversal of 231979991 is 199979132.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-231979991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231972991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115989995 + 115989996.

It is an arithmetic number, because the mean of its divisors is an integer number (115989996).

Almost surely, 2^231979991 is an apocalyptic number.

231979991 is a deficient number, since it is larger than the sum of its proper divisors (1).

231979991 is an equidigital number, since it uses as much as digits as its factorization.

231979991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 275562, while the sum is 50.

The square root of 231979991 is about 15230.8893699613. The cubic root of 231979991 is about 614.4456996904.

The spelling of 231979991 in words is "two hundred thirty-one million, nine hundred seventy-nine thousand, nine hundred ninety-one".