643971 has 4 divisors (see below), whose sum is σ = 858632. Its totient is φ = 429312.

The previous prime is 643969. The next prime is 643991. The reversal of 643971 is 179346.

It is a happy number.

643971 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 643971 - 2¹ = 643969 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643961) 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, 107326 + ... + 107331.

It is an arithmetic number, because the mean of its divisors is an integer number (214658).

2⁶⁴³⁹⁷¹ is an apocalyptic number.

643971 is a deficient number, since it is larger than the sum of its proper divisors (214661).

643971 is a wasteful number, since it uses less digits than its factorization.

643971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214660.

The product of its digits is 4536, while the sum is 30.

The square root of 643971 is about 802.4780370826. The cubic root of 643971 is about 86.3552548233.

The spelling of 643971 in words is "six hundred forty-three thousand, nine hundred seventy-one".