666139399 has 2 divisors, whose sum is σ = 666139400. Its totient is φ = 666139398.

The previous prime is 666139391. The next prime is 666139417. The reversal of 666139399 is 993931666.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666139399 - 2³ = 666139391 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666139391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333069699 + 333069700.

It is an arithmetic number, because the mean of its divisors is an integer number (333069700).

Almost surely, 2^666139399 is an apocalyptic number.

666139399 is a deficient number, since it is larger than the sum of its proper divisors (1).

666139399 is an equidigital number, since it uses as much as digits as its factorization.

666139399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1417176, while the sum is 52.

The square root of 666139399 is about 25809.6764605835. The cubic root of 666139399 is about 873.3500986267.

The spelling of 666139399 in words is "six hundred sixty-six million, one hundred thirty-nine thousand, three hundred ninety-nine".