643981172 has 6 divisors (see below), whose sum is σ = 1126967058. Its totient is φ = 321990584.

The previous prime is 643981159. The next prime is 643981211. The reversal of 643981172 is 271189346.

It can be written as a sum of positive squares in only one way, i.e., 627302116 + 16679056 = 25046^2 + 4084^2 .

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, 80497643 + ... + 80497650.

It is an arithmetic number, because the mean of its divisors is an integer number (187827843).

Almost surely, 2^643981172 is an apocalyptic number.

It is an amenable number.

643981172 is a deficient number, since it is larger than the sum of its proper divisors (482985886).

643981172 is a wasteful number, since it uses less digits than its factorization.

643981172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160995297 (or 160995295 counting only the distinct ones).

The product of its digits is 72576, while the sum is 41.

The square root of 643981172 is about 25376.7841146194. The cubic root of 643981172 is about 863.5570950269.

The spelling of 643981172 in words is "six hundred forty-three million, nine hundred eighty-one thousand, one hundred seventy-two".