644639390 has 16 divisors (see below), whose sum is σ = 1161065232. Its totient is φ = 257697024.

The previous prime is 644639363. The next prime is 644639417. The reversal of 644639390 is 93936446.

It is an interprime number because it is at equal distance from previous prime (644639363) and next prime (644639417).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2024 + ... + 35963.

It is an arithmetic number, because the mean of its divisors is an integer number (72566577).

Almost surely, 2^644639390 is an apocalyptic number.

644639390 is a deficient number, since it is larger than the sum of its proper divisors (516425842).

644639390 is a wasteful number, since it uses less digits than its factorization.

644639390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39691.

The product of its (nonzero) digits is 419904, while the sum is 44.

The square root of 644639390 is about 25389.7497033744. The cubic root of 644639390 is about 863.8512109112.

The spelling of 644639390 in words is "six hundred forty-four million, six hundred thirty-nine thousand, three hundred ninety".