644166661446 has 64 divisors (see below), whose sum is σ = 1784704181760. Its totient is φ = 167316014880.

The previous prime is 644166661441. The next prime is 644166661459.

644166661446 is nontrivially palindromic in base 10.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a junction number, because it is equal to n+sod(n) for n = 644166661392 and 644166661401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644166661441) 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, 77456961 + ... + 77465276.

It is an arithmetic number, because the mean of its divisors is an integer number (27886002840).

Almost surely, 2^644166661446 is an apocalyptic number.

644166661446 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

644166661446 is an abundant number, since it is smaller than the sum of its proper divisors (1140537520314).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644166661446 is a wasteful number, since it uses less digits than its factorization.

644166661446 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154922266 (or 154922260 counting only the distinct ones).

The product of its digits is 11943936, while the sum is 54.

The spelling of 644166661446 in words is "six hundred forty-four billion, one hundred sixty-six million, six hundred sixty-one thousand, four hundred forty-six".