644402723 has 4 divisors (see below), whose sum is σ = 644538288. Its totient is φ = 644267160.

The previous prime is 644402713. The next prime is 644402743. The reversal of 644402723 is 327204446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 327204446 = 2 ⋅163602223.

It is a cyclic number.

It is not a de Polignac number, because 644402723 - 2¹⁰ = 644401699 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 644402723.

It is not an unprimeable number, because it can be changed into a prime (644402713) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 60383 + ... + 70248.

It is an arithmetic number, because the mean of its divisors is an integer number (161134572).

Almost surely, 2^644402723 is an apocalyptic number.

644402723 is a deficient number, since it is larger than the sum of its proper divisors (135565).

644402723 is a wasteful number, since it uses less digits than its factorization.

644402723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135564.

The product of its (nonzero) digits is 32256, while the sum is 32.

The square root of 644402723 is about 25385.0885954727. The cubic root of 644402723 is about 863.7454824982.

The spelling of 644402723 in words is "six hundred forty-four million, four hundred two thousand, seven hundred twenty-three".