644260109 has 2 divisors, whose sum is σ = 644260110. Its totient is φ = 644260108.

The previous prime is 644260091. The next prime is 644260139. The reversal of 644260109 is 901062446.

It is a happy number.

Together with previous prime (644260091) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 435890884 + 208369225 = 20878^2 + 14435^2 .

It is a cyclic number.

It is not a de Polignac number, because 644260109 - 2²⁴ = 627482893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644260139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322130054 + 322130055.

It is an arithmetic number, because the mean of its divisors is an integer number (322130055).

Almost surely, 2^644260109 is an apocalyptic number.

It is an amenable number.

644260109 is a deficient number, since it is larger than the sum of its proper divisors (1).

644260109 is an equidigital number, since it uses as much as digits as its factorization.

644260109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10368, while the sum is 32.

The square root of 644260109 is about 25382.2794287668. The cubic root of 644260109 is about 863.6817587417.

The spelling of 644260109 in words is "six hundred forty-four million, two hundred sixty thousand, one hundred nine".