1666685399 has 2 divisors, whose sum is σ = 1666685400. Its totient is φ = 1666685398.

The previous prime is 1666685351. The next prime is 1666685407. The reversal of 1666685399 is 9935866661.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1666685399 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1666685299) 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, 833342699 + 833342700.

It is an arithmetic number, because the mean of its divisors is an integer number (833342700).

Almost surely, 2^1666685399 is an apocalyptic number.

1666685399 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666685399 is an equidigital number, since it uses as much as digits as its factorization.

1666685399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12597120, while the sum is 59.

The square root of 1666685399 is about 40825.0584690335. The cubic root of 1666685399 is about 1185.6355434074.

The spelling of 1666685399 in words is "one billion, six hundred sixty-six million, six hundred eighty-five thousand, three hundred ninety-nine".