643873971 has 32 divisors (see below), whose sum is σ = 950564160. Its totient is φ = 385228800.

The previous prime is 643873949. The next prime is 643873981. The reversal of 643873971 is 179378346.

643873971 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 643873971 - 2⁶ = 643873907 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 643873971.

It is not an unprimeable number, because it can be changed into a prime (643873981) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 210211 + ... + 213251.

It is an arithmetic number, because the mean of its divisors is an integer number (29705130).

Almost surely, 2^643873971 is an apocalyptic number.

643873971 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

643873971 is a deficient number, since it is larger than the sum of its proper divisors (306690189).

643873971 is a wasteful number, since it uses less digits than its factorization.

643873971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3207.

The product of its digits is 762048, while the sum is 48.

The square root of 643873971 is about 25374.6718402426. The cubic root of 643873971 is about 863.5091747225.

The spelling of 643873971 in words is "six hundred forty-three million, eight hundred seventy-three thousand, nine hundred seventy-one".