643866871 has 2 divisors, whose sum is σ = 643866872. Its totient is φ = 643866870.

The previous prime is 643866809. The next prime is 643866877. The reversal of 643866871 is 178668346.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643866871 - 2¹³ = 643858679 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643866877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321933435 + 321933436.

It is an arithmetic number, because the mean of its divisors is an integer number (321933436).

Almost surely, 2^643866871 is an apocalyptic number.

643866871 is a deficient number, since it is larger than the sum of its proper divisors (1).

643866871 is an equidigital number, since it uses as much as digits as its factorization.

643866871 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1161216, while the sum is 49.

The square root of 643866871 is about 25374.5319365698. The cubic root of 643866871 is about 863.5060007382.

The spelling of 643866871 in words is "six hundred forty-three million, eight hundred sixty-six thousand, eight hundred seventy-one".