644165543326 has 16 divisors (see below), whose sum is σ = 987031241280. Its totient is φ = 315158247040.

The previous prime is 644165543323. The next prime is 644165543339. The reversal of 644165543326 is 623345561446.

It is a self number, because there is not a number n which added to its sum of digits gives 644165543326.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644165543323) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 362695 + ... + 1191586.

It is an arithmetic number, because the mean of its divisors is an integer number (61689452580).

Almost surely, 2^644165543326 is an apocalyptic number.

644165543326 is a deficient number, since it is larger than the sum of its proper divisors (342865697954).

644165543326 is a wasteful number, since it uses less digits than its factorization.

644165543326 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1558739.

The product of its digits is 6220800, while the sum is 49.

The spelling of 644165543326 in words is "six hundred forty-four billion, one hundred sixty-five million, five hundred forty-three thousand, three hundred twenty-six".