644693841631 has 4 divisors (see below), whose sum is σ = 736792961872. Its totient is φ = 552594721392.

The previous prime is 644693841619. The next prime is 644693841641. The reversal of 644693841631 is 136148396446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 136148396446 = 2 ⋅68074198223.

It is not a de Polignac number, because 644693841631 - 2²⁹ = 644156970719 is a prime.

It is a super-2 number, since 2×644693841631² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644693841641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46049560110 + ... + 46049560123.

It is an arithmetic number, because the mean of its divisors is an integer number (184198240468).

Almost surely, 2^644693841631 is an apocalyptic number.

644693841631 is a deficient number, since it is larger than the sum of its proper divisors (92099120241).

644693841631 is an equidigital number, since it uses as much as digits as its factorization.

644693841631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92099120240.

The product of its digits is 8957952, while the sum is 55.

The spelling of 644693841631 in words is "six hundred forty-four billion, six hundred ninety-three million, eight hundred forty-one thousand, six hundred thirty-one".