643958279 has 4 divisors (see below), whose sum is σ = 677850840. Its totient is φ = 610065720.

The previous prime is 643958267. The next prime is 643958291. The reversal of 643958279 is 972859346.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (643958267) and next prime (643958291).

It is a cyclic number.

It is not a de Polignac number, because 643958279 - 2⁸ = 643958023 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 643958279.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643958299) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16946252 + ... + 16946289.

It is an arithmetic number, because the mean of its divisors is an integer number (169462710).

Almost surely, 2^643958279 is an apocalyptic number.

643958279 is a deficient number, since it is larger than the sum of its proper divisors (33892561).

643958279 is a wasteful number, since it uses less digits than its factorization.

643958279 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33892560.

The product of its digits is 3265920, while the sum is 53.

The square root of 643958279 is about 25376.3330487287. Note that the first 3 decimals coincide. The cubic root of 643958279 is about 863.5468619913.

The spelling of 643958279 in words is "six hundred forty-three million, nine hundred fifty-eight thousand, two hundred seventy-nine".