668401999 has 2 divisors, whose sum is σ = 668402000. Its totient is φ = 668401998.

The previous prime is 668401991. The next prime is 668402029. The reversal of 668401999 is 999104866.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 668401999 - 2³ = 668401991 is a prime.

It is a super-2 number, since 2×668401999² = 893522464534392002, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668401991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334200999 + 334201000.

It is an arithmetic number, because the mean of its divisors is an integer number (334201000).

Almost surely, 2^668401999 is an apocalyptic number.

668401999 is a deficient number, since it is larger than the sum of its proper divisors (1).

668401999 is an equidigital number, since it uses as much as digits as its factorization.

668401999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 839808, while the sum is 52.

The square root of 668401999 is about 25853.4717011082. The cubic root of 668401999 is about 874.3377842285.

The spelling of 668401999 in words is "six hundred sixty-eight million, four hundred one thousand, nine hundred ninety-nine".