643666612544 has 28 divisors (see below), whose sum is σ = 1277838157044. Its totient is φ = 321691643904.

The previous prime is 643666612543. The next prime is 643666612559. The reversal of 643666612544 is 445216666346.

It can be written as a sum of positive squares in 2 ways, for example, as 573594169600 + 70072442944 = 757360^2 + 264712^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643666612543) 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, 2066867 + ... + 2357810.

Almost surely, 2^643666612544 is an apocalyptic number.

643666612544 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

643666612544 is a deficient number, since it is larger than the sum of its proper divisors (634171544500).

643666612544 is a wasteful number, since it uses less digits than its factorization.

643666612544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4426962 (or 4426952 counting only the distinct ones).

The product of its digits is 14929920, while the sum is 53.

The spelling of 643666612544 in words is "six hundred forty-three billion, six hundred sixty-six million, six hundred twelve thousand, five hundred forty-four".