643621843 has 2 divisors, whose sum is σ = 643621844. Its totient is φ = 643621842.

The previous prime is 643621831. The next prime is 643621859. The reversal of 643621843 is 348126346.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643621843 is a prime.

It is not a weakly prime, because it can be changed into another prime (643621883) 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, 321810921 + 321810922.

It is an arithmetic number, because the mean of its divisors is an integer number (321810922).

Almost surely, 2^643621843 is an apocalyptic number.

643621843 is a deficient number, since it is larger than the sum of its proper divisors (1).

643621843 is an equidigital number, since it uses as much as digits as its factorization.

643621843 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 82944, while the sum is 37.

The square root of 643621843 is about 25369.7032501368. The cubic root of 643621843 is about 863.3964491091.

The spelling of 643621843 in words is "six hundred forty-three million, six hundred twenty-one thousand, eight hundred forty-three".