644747247 has 24 divisors (see below), whose sum is σ = 987743328. Its totient is φ = 404395200.

The previous prime is 644747161. The next prime is 644747261. The reversal of 644747247 is 742747446.

It is not a de Polignac number, because 644747247 - 2⁷ = 644747119 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644747267) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12904 + ... + 38157.

It is an arithmetic number, because the mean of its divisors is an integer number (41155972).

Almost surely, 2^644747247 is an apocalyptic number.

644747247 is a deficient number, since it is larger than the sum of its proper divisors (342996081).

644747247 is a wasteful number, since it uses less digits than its factorization.

644747247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51151 (or 51148 counting only the distinct ones).

The product of its digits is 1053696, while the sum is 45.

The square root of 644747247 is about 25391.8736409899. The cubic root of 644747247 is about 863.8993862713.

The spelling of 644747247 in words is "six hundred forty-four million, seven hundred forty-seven thousand, two hundred forty-seven".