643571 has 4 divisors (see below), whose sum is σ = 657312. Its totient is φ = 629832.

The previous prime is 643567. The next prime is 643583. The reversal of 643571 is 175346.

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

It is a cyclic number.

It is not a de Polignac number, because 643571 - 2² = 643567 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643571.

It is not an unprimeable number, because it can be changed into a prime (645571) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6800 + ... + 6893.

It is an arithmetic number, because the mean of its divisors is an integer number (164328).

2⁶⁴³⁵⁷¹ is an apocalyptic number.

643571 is a deficient number, since it is larger than the sum of its proper divisors (13741).

643571 is a wasteful number, since it uses less digits than its factorization.

643571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13740.

The product of its digits is 2520, while the sum is 26.

The square root of 643571 is about 802.2287703642. The cubic root of 643571 is about 86.3373713802.

Subtracting from 643571 its sum of digits (26), we obtain a triangular number (643545 = T₁₁₃₄).

The spelling of 643571 in words is "six hundred forty-three thousand, five hundred seventy-one".