66221399 has 2 divisors, whose sum is σ = 66221400. Its totient is φ = 66221398.

The previous prime is 66221381. The next prime is 66221497. The reversal of 66221399 is 99312266.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 66221399 - 2⁸ = 66221143 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66221329) 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, 33110699 + 33110700.

It is an arithmetic number, because the mean of its divisors is an integer number (33110700).

Almost surely, 2^66221399 is an apocalyptic number.

66221399 is a deficient number, since it is larger than the sum of its proper divisors (1).

66221399 is an equidigital number, since it uses as much as digits as its factorization.

66221399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34992, while the sum is 38.

The square root of 66221399 is about 8137.6531629211. The cubic root of 66221399 is about 404.5753797881.

The spelling of 66221399 in words is "sixty-six million, two hundred twenty-one thousand, three hundred ninety-nine".