643171921 has 16 divisors (see below), whose sum is σ = 751478400. Its totient is φ = 539071488.

The previous prime is 643171913. The next prime is 643171937. The reversal of 643171921 is 129171346.

It is a cyclic number.

It is not a de Polignac number, because 643171921 - 2³ = 643171913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643171901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 75675 + ... + 83743.

It is an arithmetic number, because the mean of its divisors is an integer number (46967400).

Almost surely, 2^643171921 is an apocalyptic number.

It is an amenable number.

643171921 is a deficient number, since it is larger than the sum of its proper divisors (108306479).

643171921 is a wasteful number, since it uses less digits than its factorization.

643171921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8328.

The product of its digits is 9072, while the sum is 34.

The square root of 643171921 is about 25360.8343908476. The cubic root of 643171921 is about 863.1952172760.

The spelling of 643171921 in words is "six hundred forty-three million, one hundred seventy-one thousand, nine hundred twenty-one".