644195161 has 9 divisors (see below), whose sum is σ = 684776701. Its totient is φ = 605895232.

The previous prime is 644195147. The next prime is 644195173. The reversal of 644195161 is 161591446.

The square root of 644195161 is 25381.

It is a perfect power (a square), and thus also a powerful number.

644195161 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 277855561 + 366339600 = 16669^2 + 19140^2 .

It is a de Polignac number, because none of the positive numbers 2^k-644195161 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644195161.

It is not an unprimeable number, because it can be changed into a prime (644195131) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 430731 + ... + 432223.

Almost surely, 2^644195161 is an apocalyptic number.

644195161 is the 25381-st square number.

644195161 is the 12691-st centered octagonal number.

It is an amenable number.

644195161 is a deficient number, since it is larger than the sum of its proper divisors (40581540).

644195161 is an frugal number, since it uses more digits than its factorization.

644195161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3020 (or 1510 counting only the distinct ones).

The product of its digits is 25920, while the sum is 37.

The cubic root of 644195161 is about 863.6527351185.

The spelling of 644195161 in words is "six hundred forty-four million, one hundred ninety-five thousand, one hundred sixty-one".