644189306 has 4 divisors (see below), whose sum is σ = 966283962. Its totient is φ = 322094652.

The previous prime is 644189263. The next prime is 644189309. The reversal of 644189306 is 603981446.

644189306 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 603981446 = 2 ⋅301990723.

It can be written as a sum of positive squares in only one way, i.e., 624750025 + 19439281 = 24995^2 + 4409^2 .

It is not an unprimeable number, because it can be changed into a prime (644189309) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161047325 + ... + 161047328.

Almost surely, 2^644189306 is an apocalyptic number.

644189306 is a deficient number, since it is larger than the sum of its proper divisors (322094656).

644189306 is a wasteful number, since it uses less digits than its factorization.

644189306 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322094655.

The product of its (nonzero) digits is 124416, while the sum is 41.

The square root of 644189306 is about 25380.8846575528. The cubic root of 644189306 is about 863.6501185708.

The spelling of 644189306 in words is "six hundred forty-four million, one hundred eighty-nine thousand, three hundred six".