644166320655 has 32 divisors (see below), whose sum is σ = 1210852500480. Its totient is φ = 288298212480.

The previous prime is 644166320641. The next prime is 644166320657. The reversal of 644166320655 is 556023661446.

644166320655 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644166320655 - 2⁴ = 644166320639 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644166320657) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 150153175 + ... + 150157464.

It is an arithmetic number, because the mean of its divisors is an integer number (37839140640).

Almost surely, 2^644166320655 is an apocalyptic number.

644166320655 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

644166320655 is a deficient number, since it is larger than the sum of its proper divisors (566686179825).

644166320655 is a wasteful number, since it uses less digits than its factorization.

644166320655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300310671.

The product of its (nonzero) digits is 3110400, while the sum is 48.

The spelling of 644166320655 in words is "six hundred forty-four billion, one hundred sixty-six million, three hundred twenty thousand, six hundred fifty-five".