644122109 has 2 divisors, whose sum is σ = 644122110. Its totient is φ = 644122108.

The previous prime is 644122099. The next prime is 644122133. The reversal of 644122109 is 901221446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 624850009 + 19272100 = 24997^2 + 4390^2 .

It is a cyclic number.

It is not a de Polignac number, because 644122109 - 2²⁰ = 643073533 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644122189) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322061054 + 322061055.

It is an arithmetic number, because the mean of its divisors is an integer number (322061055).

Almost surely, 2^644122109 is an apocalyptic number.

It is an amenable number.

644122109 is a deficient number, since it is larger than the sum of its proper divisors (1).

644122109 is an equidigital number, since it uses as much as digits as its factorization.

644122109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 644122109 is about 25379.5608512047. The cubic root of 644122109 is about 863.6200876909.

The spelling of 644122109 in words is "six hundred forty-four million, one hundred twenty-two thousand, one hundred nine".