668259491 has 2 divisors, whose sum is σ = 668259492. Its totient is φ = 668259490.

The previous prime is 668259463. The next prime is 668259497. The reversal of 668259491 is 194952866.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 668259491 - 2²² = 664065187 is a prime.

It is not a weakly prime, because it can be changed into another prime (668259497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334129745 + 334129746.

It is an arithmetic number, because the mean of its divisors is an integer number (334129746).

Almost surely, 2^668259491 is an apocalyptic number.

668259491 is a deficient number, since it is larger than the sum of its proper divisors (1).

668259491 is an equidigital number, since it uses as much as digits as its factorization.

668259491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 933120, while the sum is 50.

The square root of 668259491 is about 25850.7154833285. The cubic root of 668259491 is about 874.2756414934.

The spelling of 668259491 in words is "six hundred sixty-eight million, two hundred fifty-nine thousand, four hundred ninety-one".