311005991 has 2 divisors, whose sum is σ = 311005992. Its totient is φ = 311005990.

The previous prime is 311005987. The next prime is 311005993. The reversal of 311005991 is 199500113.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 311005991 - 2² = 311005987 is a prime.

Together with 311005993, 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 (311005993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 155502995 + 155502996.

It is an arithmetic number, because the mean of its divisors is an integer number (155502996).

Almost surely, 2^311005991 is an apocalyptic number.

311005991 is a deficient number, since it is larger than the sum of its proper divisors (1).

311005991 is an equidigital number, since it uses as much as digits as its factorization.

311005991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1215, while the sum is 29.

The square root of 311005991 is about 17635.3619469519. The cubic root of 311005991 is about 677.5212456857.

The spelling of 311005991 in words is "three hundred eleven million, five thousand, nine hundred ninety-one".