644759709 has 16 divisors (see below), whose sum is σ = 946942464. Its totient is φ = 386967600.

The previous prime is 644759683. The next prime is 644759723. The reversal of 644759709 is 907957446.

It is not a de Polignac number, because 644759709 - 2⁹ = 644759197 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644759789) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91447 + ... + 98244.

It is an arithmetic number, because the mean of its divisors is an integer number (59183904).

Almost surely, 2^644759709 is an apocalyptic number.

It is an amenable number.

644759709 is a deficient number, since it is larger than the sum of its proper divisors (302182755).

644759709 is a wasteful number, since it uses less digits than its factorization.

644759709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189808.

The product of its (nonzero) digits is 1905120, while the sum is 51.

The square root of 644759709 is about 25392.1190332749. The cubic root of 644759709 is about 863.9049521964.

The spelling of 644759709 in words is "six hundred forty-four million, seven hundred fifty-nine thousand, seven hundred nine".