644486771 has 4 divisors (see below), whose sum is σ = 649191192. Its totient is φ = 639782352.

The previous prime is 644486743. The next prime is 644486803. The reversal of 644486771 is 177684446.

644486771 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: 177684446 = 2 ⋅88842223.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644486771 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644486741) 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, 2352005 + ... + 2352278.

It is an arithmetic number, because the mean of its divisors is an integer number (162297798).

Almost surely, 2^644486771 is an apocalyptic number.

644486771 is a deficient number, since it is larger than the sum of its proper divisors (4704421).

644486771 is a wasteful number, since it uses less digits than its factorization.

644486771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4704420.

The product of its digits is 903168, while the sum is 47.

The square root of 644486771 is about 25386.7440015454. The cubic root of 644486771 is about 863.7830329935.

The spelling of 644486771 in words is "six hundred forty-four million, four hundred eighty-six thousand, seven hundred seventy-one".