643403993 has 2 divisors, whose sum is σ = 643403994. Its totient is φ = 643403992.

The previous prime is 643403963. The next prime is 643404017. The reversal of 643403993 is 399304346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 367412224 + 275991769 = 19168^2 + 16613^2 .

It is a cyclic number.

It is not a de Polignac number, because 643403993 - 2¹⁶ = 643338457 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 643403993.

It is not a weakly prime, because it can be changed into another prime (643403933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321701996 + 321701997.

It is an arithmetic number, because the mean of its divisors is an integer number (321701997).

Almost surely, 2^643403993 is an apocalyptic number.

It is an amenable number.

643403993 is a deficient number, since it is larger than the sum of its proper divisors (1).

643403993 is an equidigital number, since it uses as much as digits as its factorization.

643403993 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 209952, while the sum is 41.

The square root of 643403993 is about 25365.4093797045. The cubic root of 643403993 is about 863.2990253688.

The spelling of 643403993 in words is "six hundred forty-three million, four hundred three thousand, nine hundred ninety-three".