643440439 has 2 divisors, whose sum is σ = 643440440. Its totient is φ = 643440438.

The previous prime is 643440401. The next prime is 643440443. The reversal of 643440439 is 934044346.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643440439 - 2⁷ = 643440311 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 643440398 and 643440407.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643441439) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321720219 + 321720220.

It is an arithmetic number, because the mean of its divisors is an integer number (321720220).

Almost surely, 2^643440439 is an apocalyptic number.

643440439 is a deficient number, since it is larger than the sum of its proper divisors (1).

643440439 is an equidigital number, since it uses as much as digits as its factorization.

643440439 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 124416, while the sum is 37.

The square root of 643440439 is about 25366.1277888447. The cubic root of 643440439 is about 863.3153257558.

The spelling of 643440439 in words is "six hundred forty-three million, four hundred forty thousand, four hundred thirty-nine".