667691 has 2 divisors, whose sum is σ = 667692. Its totient is φ = 667690.

The previous prime is 667687. The next prime is 667697. The reversal of 667691 is 196766.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 667691 - 2² = 667687 is a prime.

It is a super-2 number, since 2×667691² = 891622542962, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (667697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333845 + 333846.

It is an arithmetic number, because the mean of its divisors is an integer number (333846).

2⁶⁶⁷⁶⁹¹ is an apocalyptic number.

667691 is a deficient number, since it is larger than the sum of its proper divisors (1).

667691 is an equidigital number, since it uses as much as digits as its factorization.

667691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13608, while the sum is 35.

The square root of 667691 is about 817.1236136595. The cubic root of 667691 is about 87.4027654573.

The spelling of 667691 in words is "six hundred sixty-seven thousand, six hundred ninety-one".