643868518 has 4 divisors (see below), whose sum is σ = 965802780. Its totient is φ = 321934258.

The previous prime is 643868513. The next prime is 643868567. The reversal of 643868518 is 815868346.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643868513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160967128 + ... + 160967131.

It is an arithmetic number, because the mean of its divisors is an integer number (241450695).

Almost surely, 2^643868518 is an apocalyptic number.

643868518 is a deficient number, since it is larger than the sum of its proper divisors (321934262).

643868518 is a wasteful number, since it uses less digits than its factorization.

643868518 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321934261.

The product of its digits is 1105920, while the sum is 49.

The square root of 643868518 is about 25374.5643903496. The cubic root of 643868518 is about 863.5067370152.

The spelling of 643868518 in words is "six hundred forty-three million, eight hundred sixty-eight thousand, five hundred eighteen".