668867819 has 2 divisors, whose sum is σ = 668867820. Its totient is φ = 668867818.

The previous prime is 668867813. The next prime is 668867821. The reversal of 668867819 is 918768866.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-668867819 is a prime.

It is a super-2 number, since 2×668867819² = 894768318587633522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 668867821, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (668867813) 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, 334433909 + 334433910.

It is an arithmetic number, because the mean of its divisors is an integer number (334433910).

Almost surely, 2^668867819 is an apocalyptic number.

668867819 is a deficient number, since it is larger than the sum of its proper divisors (1).

668867819 is an equidigital number, since it uses as much as digits as its factorization.

668867819 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6967296, while the sum is 59.

The square root of 668867819 is about 25862.4789801751. The cubic root of 668867819 is about 874.5408503722.

The spelling of 668867819 in words is "six hundred sixty-eight million, eight hundred sixty-seven thousand, eight hundred nineteen".