643406879 has 2 divisors, whose sum is σ = 643406880. Its totient is φ = 643406878.

The previous prime is 643406867. The next prime is 643406887. The reversal of 643406879 is 978604346.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643406879 - 2²⁰ = 642358303 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643406849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321703439 + 321703440.

It is an arithmetic number, because the mean of its divisors is an integer number (321703440).

Almost surely, 2^643406879 is an apocalyptic number.

643406879 is a deficient number, since it is larger than the sum of its proper divisors (1).

643406879 is an equidigital number, since it uses as much as digits as its factorization.

643406879 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 870912, while the sum is 47.

The square root of 643406879 is about 25365.4662681371. The cubic root of 643406879 is about 863.3003161479.

The spelling of 643406879 in words is "six hundred forty-three million, four hundred six thousand, eight hundred seventy-nine".