644102665 has 8 divisors (see below), whose sum is σ = 773073288. Its totient is φ = 515182080.

The previous prime is 644102663. The next prime is 644102677. The reversal of 644102665 is 566201446.

It can be written as a sum of positive squares in 4 ways, for example, as 82791801 + 561310864 = 9099^2 + 23692^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 644102665 - 2¹ = 644102663 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644102665.

It is not an unprimeable number, because it can be changed into a prime (644102663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27385 + ... + 45145.

It is an arithmetic number, because the mean of its divisors is an integer number (96634161).

Almost surely, 2^644102665 is an apocalyptic number.

It is an amenable number.

644102665 is a deficient number, since it is larger than the sum of its proper divisors (128970623).

644102665 is a wasteful number, since it uses less digits than its factorization.

644102665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25019.

The product of its (nonzero) digits is 34560, while the sum is 34.

The square root of 644102665 is about 25379.1777841600. The cubic root of 644102665 is about 863.6113976213.

The spelling of 644102665 in words is "six hundred forty-four million, one hundred two thousand, six hundred sixty-five".