644031605993 has 2 divisors, whose sum is σ = 644031605994. Its totient is φ = 644031605992.

The previous prime is 644031605983. The next prime is 644031606013. The reversal of 644031605993 is 399506130446.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 586445045209 + 57586560784 = 765797^2 + 239972^2 .

It is a cyclic number.

It is not a de Polignac number, because 644031605993 - 2³⁶ = 575312129257 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (644031605963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322015802996 + 322015802997.

It is an arithmetic number, because the mean of its divisors is an integer number (322015802997).

Almost surely, 2^644031605993 is an apocalyptic number.

It is an amenable number.

644031605993 is a deficient number, since it is larger than the sum of its proper divisors (1).

644031605993 is an equidigital number, since it uses as much as digits as its factorization.

644031605993 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2099520, while the sum is 50.

The spelling of 644031605993 in words is "six hundred forty-four billion, thirty-one million, six hundred five thousand, nine hundred ninety-three".