668617931 has 2 divisors, whose sum is σ = 668617932. Its totient is φ = 668617930.

The previous prime is 668617927. The next prime is 668617933. The reversal of 668617931 is 139716866.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 668617931 - 2² = 668617927 is a prime.

It is a super-2 number, since 2×668617931² = 894099875309441522, which contains 22 as substring.

Together with 668617933, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (668617933) 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, 334308965 + 334308966.

It is an arithmetic number, because the mean of its divisors is an integer number (334308966).

Almost surely, 2^668617931 is an apocalyptic number.

668617931 is a deficient number, since it is larger than the sum of its proper divisors (1).

668617931 is an equidigital number, since it uses as much as digits as its factorization.

668617931 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 47.

The square root of 668617931 is about 25857.6474374604. The cubic root of 668617931 is about 874.4319277627.

The spelling of 668617931 in words is "six hundred sixty-eight million, six hundred seventeen thousand, nine hundred thirty-one".