668891539 has 2 divisors, whose sum is σ = 668891540. Its totient is φ = 668891538.

The previous prime is 668891521. The next prime is 668891549. The reversal of 668891539 is 935198866.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 668891539 - 2⁷ = 668891411 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 668891539.

It is not a weakly prime, because it can be changed into another prime (668891519) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334445769 + 334445770.

It is an arithmetic number, because the mean of its divisors is an integer number (334445770).

Almost surely, 2^668891539 is an apocalyptic number.

668891539 is a deficient number, since it is larger than the sum of its proper divisors (1).

668891539 is an equidigital number, since it uses as much as digits as its factorization.

668891539 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2799360, while the sum is 55.

The square root of 668891539 is about 25862.9375555059. The cubic root of 668891539 is about 874.5511881714.

The spelling of 668891539 in words is "six hundred sixty-eight million, eight hundred ninety-one thousand, five hundred thirty-nine".