644599889 has 2 divisors, whose sum is σ = 644599890. Its totient is φ = 644599888.

The previous prime is 644599873. The next prime is 644599913. The reversal of 644599889 is 988995446.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 410265025 + 234334864 = 20255^2 + 15308^2 .

It is a cyclic number.

It is not a de Polignac number, because 644599889 - 2⁴ = 644599873 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644593889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322299944 + 322299945.

It is an arithmetic number, because the mean of its divisors is an integer number (322299945).

Almost surely, 2^644599889 is an apocalyptic number.

It is an amenable number.

644599889 is a deficient number, since it is larger than the sum of its proper divisors (1).

644599889 is an equidigital number, since it uses as much as digits as its factorization.

644599889 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22394880, while the sum is 62.

The square root of 644599889 is about 25388.9717987948. The cubic root of 644599889 is about 863.8335660676.

The spelling of 644599889 in words is "six hundred forty-four million, five hundred ninety-nine thousand, eight hundred eighty-nine".