644266723 has 4 divisors (see below), whose sum is σ = 645395608. Its totient is φ = 643137840.

The previous prime is 644266699. The next prime is 644266739. The reversal of 644266723 is 327662446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 327662446 = 2 ⋅163831223.

It is a cyclic number.

It is not a de Polignac number, because 644266723 - 2¹⁷ = 644135651 is a prime.

It is a super-2 number, since 2×644266723² = 830159220730317458, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644266793) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 563586 + ... + 564727.

It is an arithmetic number, because the mean of its divisors is an integer number (161348902).

Almost surely, 2^644266723 is an apocalyptic number.

644266723 is a deficient number, since it is larger than the sum of its proper divisors (1128885).

644266723 is a wasteful number, since it uses less digits than its factorization.

644266723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1128884.

The product of its digits is 290304, while the sum is 40.

The square root of 644266723 is about 25382.4097161794. The cubic root of 644266723 is about 863.6847142621.

The spelling of 644266723 in words is "six hundred forty-four million, two hundred sixty-six thousand, seven hundred twenty-three".