666521423 has 2 divisors, whose sum is σ = 666521424. Its totient is φ = 666521422.

The previous prime is 666521389. The next prime is 666521437. The reversal of 666521423 is 324125666.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-666521423 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666521473) 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, 333260711 + 333260712.

It is an arithmetic number, because the mean of its divisors is an integer number (333260712).

Almost surely, 2^666521423 is an apocalyptic number.

666521423 is a deficient number, since it is larger than the sum of its proper divisors (1).

666521423 is an equidigital number, since it uses as much as digits as its factorization.

666521423 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 51840, while the sum is 35.

The square root of 666521423 is about 25817.0761899949. The cubic root of 666521423 is about 873.5170191136.

The spelling of 666521423 in words is "six hundred sixty-six million, five hundred twenty-one thousand, four hundred twenty-three".