643887823 has 2 divisors, whose sum is σ = 643887824. Its totient is φ = 643887822.

The previous prime is 643887817. The next prime is 643887833. The reversal of 643887823 is 328788346.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643887823 - 2⁵ = 643887791 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643887833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321943911 + 321943912.

It is an arithmetic number, because the mean of its divisors is an integer number (321943912).

Almost surely, 2^643887823 is an apocalyptic number.

643887823 is a deficient number, since it is larger than the sum of its proper divisors (1).

643887823 is an equidigital number, since it uses as much as digits as its factorization.

643887823 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1548288, while the sum is 49.

The square root of 643887823 is about 25374.9447881173. The cubic root of 643887823 is about 863.5153670540.

The spelling of 643887823 in words is "six hundred forty-three million, eight hundred eighty-seven thousand, eight hundred twenty-three".