643533646544 has 10 divisors (see below), whose sum is σ = 1246846440210. Its totient is φ = 321766823264.

The previous prime is 643533646529. The next prime is 643533646577. The reversal of 643533646544 is 445646335346.

It can be written as a sum of positive squares in only one way, i.e., 602194624144 + 41339022400 = 776012^2 + 203320^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20110426439 + ... + 20110426470.

It is an arithmetic number, because the mean of its divisors is an integer number (124684644021).

Almost surely, 2^643533646544 is an apocalyptic number.

It is an amenable number.

643533646544 is a deficient number, since it is larger than the sum of its proper divisors (603312793666).

643533646544 is a wasteful number, since it uses less digits than its factorization.

643533646544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40220852917 (or 40220852911 counting only the distinct ones).

The product of its digits is 37324800, while the sum is 53.

The spelling of 643533646544 in words is "six hundred forty-three billion, five hundred thirty-three million, six hundred forty-six thousand, five hundred forty-four".