644802271 has 4 divisors (see below), whose sum is σ = 644866272. Its totient is φ = 644738272.

The previous prime is 644802251. The next prime is 644802283. The reversal of 644802271 is 172208446.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 644802271 - 2⁷ = 644802143 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644802251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13210 + ... + 38263.

It is an arithmetic number, because the mean of its divisors is an integer number (161216568).

Almost surely, 2^644802271 is an apocalyptic number.

644802271 is a deficient number, since it is larger than the sum of its proper divisors (64001).

644802271 is a wasteful number, since it uses less digits than its factorization.

644802271 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64000.

The product of its (nonzero) digits is 21504, while the sum is 34.

The square root of 644802271 is about 25392.9571141291. The cubic root of 644802271 is about 863.9239611973.

The spelling of 644802271 in words is "six hundred forty-four million, eight hundred two thousand, two hundred seventy-one".