643755941 has 2 divisors, whose sum is σ = 643755942. Its totient is φ = 643755940.

The previous prime is 643755919. The next prime is 643755971. The reversal of 643755941 is 149557346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 486378916 + 157377025 = 22054^2 + 12545^2 .

It is a cyclic number.

It is not a de Polignac number, because 643755941 - 2¹⁴ = 643739557 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 643755892 and 643755901.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643755971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321877970 + 321877971.

It is an arithmetic number, because the mean of its divisors is an integer number (321877971).

Almost surely, 2^643755941 is an apocalyptic number.

It is an amenable number.

643755941 is a deficient number, since it is larger than the sum of its proper divisors (1).

643755941 is an equidigital number, since it uses as much as digits as its factorization.

643755941 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 453600, while the sum is 44.

The square root of 643755941 is about 25372.3459892853. The cubic root of 643755941 is about 863.4564075554.

The spelling of 643755941 in words is "six hundred forty-three million, seven hundred fifty-five thousand, nine hundred forty-one".