643963871 has 2 divisors, whose sum is σ = 643963872. Its totient is φ = 643963870.

The previous prime is 643963847. The next prime is 643963877. The reversal of 643963871 is 178369346.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643963871 - 2⁶ = 643963807 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643963877) 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, 321981935 + 321981936.

It is an arithmetic number, because the mean of its divisors is an integer number (321981936).

Almost surely, 2^643963871 is an apocalyptic number.

643963871 is a deficient number, since it is larger than the sum of its proper divisors (1).

643963871 is an equidigital number, since it uses as much as digits as its factorization.

643963871 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 653184, while the sum is 47.

The square root of 643963871 is about 25376.4432298933. The cubic root of 643963871 is about 863.5493616046.

The spelling of 643963871 in words is "six hundred forty-three million, nine hundred sixty-three thousand, eight hundred seventy-one".