644380658 has 4 divisors (see below), whose sum is σ = 966570990. Its totient is φ = 322190328.

The previous prime is 644380651. The next prime is 644380679. The reversal of 644380658 is 856083446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 856083446 = 2 ⋅428041723.

It can be written as a sum of positive squares in only one way, i.e., 472062529 + 172318129 = 21727^2 + 13127^2 .

It is not an unprimeable number, because it can be changed into a prime (644380651) 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 as a sum of consecutive naturals, namely, 161095163 + ... + 161095166.

Almost surely, 2^644380658 is an apocalyptic number.

644380658 is a deficient number, since it is larger than the sum of its proper divisors (322190332).

644380658 is a wasteful number, since it uses less digits than its factorization.

644380658 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322190331.

The product of its (nonzero) digits is 552960, while the sum is 44.

The square root of 644380658 is about 25384.6539862177. The cubic root of 644380658 is about 863.7356238798.

The spelling of 644380658 in words is "six hundred forty-four million, three hundred eighty thousand, six hundred fifty-eight".