644451665 has 32 divisors (see below), whose sum is σ = 921062016. Its totient is φ = 426677760.

The previous prime is 644451649. The next prime is 644451673. The reversal of 644451665 is 566154446.

It is not a de Polignac number, because 644451665 - 2⁴ = 644451649 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 46022 + ... + 58368.

It is an arithmetic number, because the mean of its divisors is an integer number (28783188).

Almost surely, 2^644451665 is an apocalyptic number.

644451665 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

644451665 is a deficient number, since it is larger than the sum of its proper divisors (276610351).

644451665 is a wasteful number, since it uses less digits than its factorization.

644451665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12449.

The product of its digits is 345600, while the sum is 41.

The square root of 644451665 is about 25386.0525682903. The cubic root of 644451665 is about 863.7673489283.

The spelling of 644451665 in words is "six hundred forty-four million, four hundred fifty-one thousand, six hundred sixty-five".