666639979 has 2 divisors, whose sum is σ = 666639980. Its totient is φ = 666639978.

The previous prime is 666639973. The next prime is 666640001. The reversal of 666639979 is 979936666.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666639979 - 2¹⁹ = 666115691 is a prime.

It is a super-2 number, since 2×666639979² = 888817723202240882, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (666639973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333319989 + 333319990.

It is an arithmetic number, because the mean of its divisors is an integer number (333319990).

Almost surely, 2^666639979 is an apocalyptic number.

666639979 is a deficient number, since it is larger than the sum of its proper divisors (1).

666639979 is an equidigital number, since it uses as much as digits as its factorization.

666639979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 19840464, while the sum is 61.

The square root of 666639979 is about 25819.3721651011. The cubic root of 666639979 is about 873.5688076686.

The spelling of 666639979 in words is "six hundred sixty-six million, six hundred thirty-nine thousand, nine hundred seventy-nine".