643391172 has 18 divisors (see below), whose sum is σ = 1626349998. Its totient is φ = 214463712.

The previous prime is 643391159. The next prime is 643391209. The reversal of 643391172 is 271193346.

643391172 is a `hidden beast` number, since 643 + 3 + 9 + 1 + 1 + 7 + 2 = 666.

643391172 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 513294336 + 130096836 = 22656^2 + 11406^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 17871977 = 643391172 / (6 + 4 + 3 + 3 + 9 + 1 + 1 + 7 + 2).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8935953 + ... + 8936024.

Almost surely, 2^643391172 is an apocalyptic number.

It is an amenable number.

643391172 is an abundant number, since it is smaller than the sum of its proper divisors (982958826).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

643391172 is a wasteful number, since it uses less digits than its factorization.

643391172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17871987 (or 17871982 counting only the distinct ones).

The product of its digits is 27216, while the sum is 36.

The square root of 643391172 is about 25365.1566523844. The cubic root of 643391172 is about 863.2932910607.

The spelling of 643391172 in words is "six hundred forty-three million, three hundred ninety-one thousand, one hundred seventy-two".