644663161 has 2 divisors, whose sum is σ = 644663162. Its totient is φ = 644663160.

The previous prime is 644663119. The next prime is 644663203. The reversal of 644663161 is 161366446.

It is a balanced prime because it is at equal distance from previous prime (644663119) and next prime (644663203).

It can be written as a sum of positive squares in only one way, i.e., 478253161 + 166410000 = 21869^2 + 12900^2 .

It is a cyclic number.

It is not a de Polignac number, because 644663161 - 2¹⁷ = 644532089 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644663161.

It is not a weakly prime, because it can be changed into another prime (644663101) 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, 322331580 + 322331581.

It is an arithmetic number, because the mean of its divisors is an integer number (322331581).

Almost surely, 2^644663161 is an apocalyptic number.

It is an amenable number.

644663161 is a deficient number, since it is larger than the sum of its proper divisors (1).

644663161 is an equidigital number, since it uses as much as digits as its factorization.

644663161 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 37.

The square root of 644663161 is about 25390.2178210428. The cubic root of 644663161 is about 863.8618289172.

The spelling of 644663161 in words is "six hundred forty-four million, six hundred sixty-three thousand, one hundred sixty-one".