643521644 has 6 divisors (see below), whose sum is σ = 1126162884. Its totient is φ = 321760820.

The previous prime is 643521631. The next prime is 643521661. The reversal of 643521644 is 446125346.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80440202 + ... + 80440209.

It is an arithmetic number, because the mean of its divisors is an integer number (187693814).

Almost surely, 2^643521644 is an apocalyptic number.

It is an amenable number.

643521644 is a deficient number, since it is larger than the sum of its proper divisors (482641240).

643521644 is a wasteful number, since it uses less digits than its factorization.

643521644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160880415 (or 160880413 counting only the distinct ones).

The product of its digits is 69120, while the sum is 35.

The square root of 643521644 is about 25367.7283965277. The cubic root of 643521644 is about 863.3516422858.

The spelling of 643521644 in words is "six hundred forty-three million, five hundred twenty-one thousand, six hundred forty-four".