644576538667 has 2 divisors, whose sum is σ = 644576538668. Its totient is φ = 644576538666.

The previous prime is 644576538583. The next prime is 644576538673. The reversal of 644576538667 is 766835675446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644576538667 - 2¹¹ = 644576536619 is a prime.

It is a super-2 number, since 2×644576538667² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (644576530667) 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, 322288269333 + 322288269334.

It is an arithmetic number, because the mean of its divisors is an integer number (322288269334).

Almost surely, 2^644576538667 is an apocalyptic number.

644576538667 is a deficient number, since it is larger than the sum of its proper divisors (1).

644576538667 is an equidigital number, since it uses as much as digits as its factorization.

644576538667 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 609638400, while the sum is 67.

The spelling of 644576538667 in words is "six hundred forty-four billion, five hundred seventy-six million, five hundred thirty-eight thousand, six hundred sixty-seven".