644221267 has 2 divisors, whose sum is σ = 644221268. Its totient is φ = 644221266.

The previous prime is 644221229. The next prime is 644221289. The reversal of 644221267 is 762122446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644221267 - 2⁷ = 644221139 is a prime.

It is not a weakly prime, because it can be changed into another prime (644227267) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322110633 + 322110634.

It is an arithmetic number, because the mean of its divisors is an integer number (322110634).

Almost surely, 2^644221267 is an apocalyptic number.

644221267 is a deficient number, since it is larger than the sum of its proper divisors (1).

644221267 is an equidigital number, since it uses as much as digits as its factorization.

644221267 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32256, while the sum is 34.

The square root of 644221267 is about 25381.5142771270. The cubic root of 644221267 is about 863.6644014660.

The spelling of 644221267 in words is "six hundred forty-four million, two hundred twenty-one thousand, two hundred sixty-seven".