643979933 has 2 divisors, whose sum is σ = 643979934. Its totient is φ = 643979932.

The previous prime is 643979929. The next prime is 643979969. The reversal of 643979933 is 339979346.

643979933 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 597166969 + 46812964 = 24437^2 + 6842^2 .

It is a cyclic number.

It is not a de Polignac number, because 643979933 - 2² = 643979929 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643979923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321989966 + 321989967.

It is an arithmetic number, because the mean of its divisors is an integer number (321989967).

Almost surely, 2^643979933 is an apocalyptic number.

It is an amenable number.

643979933 is a deficient number, since it is larger than the sum of its proper divisors (1).

643979933 is an equidigital number, since it uses as much as digits as its factorization.

643979933 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3306744, while the sum is 53.

The square root of 643979933 is about 25376.7597025310. The cubic root of 643979933 is about 863.5565412075.

The spelling of 643979933 in words is "six hundred forty-three million, nine hundred seventy-nine thousand, nine hundred thirty-three".