644731534 has 4 divisors (see below), whose sum is σ = 967097304. Its totient is φ = 322365766.

The previous prime is 644731489. The next prime is 644731537. The reversal of 644731534 is 435137446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 435137446 = 2 ⋅217568723.

It is a junction number, because it is equal to n+sod(n) for n = 644731493 and 644731502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644731537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161182882 + ... + 161182885.

It is an arithmetic number, because the mean of its divisors is an integer number (241774326).

Almost surely, 2^644731534 is an apocalyptic number.

644731534 is a deficient number, since it is larger than the sum of its proper divisors (322365770).

644731534 is a wasteful number, since it uses less digits than its factorization.

644731534 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322365769.

The product of its digits is 120960, while the sum is 37.

The square root of 644731534 is about 25391.5642290899. The cubic root of 644731534 is about 863.8923682440.

The spelling of 644731534 in words is "six hundred forty-four million, seven hundred thirty-one thousand, five hundred thirty-four".