643931 has 4 divisors (see below), whose sum is σ = 671952. Its totient is φ = 615912.

The previous prime is 643927. The next prime is 643949. The reversal of 643931 is 139346.

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 643931 - 2² = 643927 is a prime.

It is a super-2 number, since 2×643931² = 829294265522, which contains 22 as substring.

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 643931.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643931.

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, 13976 + ... + 14021.

It is an arithmetic number, because the mean of its divisors is an integer number (167988).

2⁶⁴³⁹³¹ is an apocalyptic number.

643931 is a deficient number, since it is larger than the sum of its proper divisors (28021).

643931 is a wasteful number, since it uses less digits than its factorization.

643931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28020.

The product of its digits is 1944, while the sum is 26.

The square root of 643931 is about 802.4531138951. The cubic root of 643931 is about 86.3534668123.

The spelling of 643931 in words is "six hundred forty-three thousand, nine hundred thirty-one".