667668691 has 2 divisors, whose sum is σ = 667668692. Its totient is φ = 667668690.

The previous prime is 667668667. The next prime is 667668713. The reversal of 667668691 is 196866766.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 667668691 - 2⁷ = 667668563 is a prime.

It is not a weakly prime, because it can be changed into another prime (667668191) 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, 333834345 + 333834346.

It is an arithmetic number, because the mean of its divisors is an integer number (333834346).

Almost surely, 2^667668691 is an apocalyptic number.

667668691 is a deficient number, since it is larger than the sum of its proper divisors (1).

667668691 is an equidigital number, since it uses as much as digits as its factorization.

667668691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3919104, while the sum is 55.

The square root of 667668691 is about 25839.2858066937. The cubic root of 667668691 is about 874.0179200804.

It can be divided in two parts, 66766 and 8691, that added together give a palindrome (75457).

The spelling of 667668691 in words is "six hundred sixty-seven million, six hundred sixty-eight thousand, six hundred ninety-one".