666619999 has 2 divisors, whose sum is σ = 666620000. Its totient is φ = 666619998.

The previous prime is 666619991. The next prime is 666620023. The reversal of 666619999 is 999916666.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666619999 - 2³ = 666619991 is a prime.

666619999 is a strobogrammatic number because it is the same when read upside-down.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666619991) 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, 333309999 + 333310000.

It is an arithmetic number, because the mean of its divisors is an integer number (333310000).

Almost surely, 2^666619999 is an apocalyptic number.

666619999 is a deficient number, since it is larger than the sum of its proper divisors (1).

666619999 is an equidigital number, since it uses as much as digits as its factorization.

666619999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8503056, while the sum is 61.

The square root of 666619999 is about 25818.9852434212. The cubic root of 666619999 is about 873.5600802797.

The spelling of 666619999 in words is "six hundred sixty-six million, six hundred nineteen thousand, nine hundred ninety-nine".