644371065 has 32 divisors (see below), whose sum is σ = 1233671040. Its totient is φ = 317227968.

The previous prime is 644371061. The next prime is 644371067. The reversal of 644371065 is 560173446.

It is a happy number.

644371065 is a `hidden beast` number, since 644 + 3 + 7 + 1 + 0 + 6 + 5 = 666.

It is not a de Polignac number, because 644371065 - 2² = 644371061 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644371061) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 181827 + ... + 185336.

It is an arithmetic number, because the mean of its divisors is an integer number (38552220).

Almost surely, 2^644371065 is an apocalyptic number.

644371065 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

644371065 is a deficient number, since it is larger than the sum of its proper divisors (589299975).

644371065 is a wasteful number, since it uses less digits than its factorization.

644371065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 367190 (or 367184 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 36.

The square root of 644371065 is about 25384.4650327715. The cubic root of 644371065 is about 863.7313376675.

The spelling of 644371065 in words is "six hundred forty-four million, three hundred seventy-one thousand, sixty-five".