666978879653 has 2 divisors, whose sum is σ = 666978879654. Its totient is φ = 666978879652.

The previous prime is 666978879647. The next prime is 666978879689. The reversal of 666978879653 is 356978879666.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 356954866849 + 310024012804 = 597457^2 + 556798^2 .

It is a cyclic number.

It is not a de Polignac number, because 666978879653 - 2³⁸ = 392100972709 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (606978879653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333489439826 + 333489439827.

It is an arithmetic number, because the mean of its divisors is an integer number (333489439827).

Almost surely, 2^666978879653 is an apocalyptic number.

It is an amenable number.

666978879653 is a deficient number, since it is larger than the sum of its proper divisors (1).

666978879653 is an equidigital number, since it uses as much as digits as its factorization.

666978879653 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4938071040, while the sum is 80.

The spelling of 666978879653 in words is "six hundred sixty-six billion, nine hundred seventy-eight million, eight hundred seventy-nine thousand, six hundred fifty-three".