643543181 has 2 divisors, whose sum is σ = 643543182. Its totient is φ = 643543180.

The previous prime is 643543171. The next prime is 643543193. The reversal of 643543181 is 181345346.

643543181 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 610584100 + 32959081 = 24710^2 + 5741^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643543181 is a prime.

It is a super-2 number, since 2×643543181² = 828295651623197522, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643543171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321771590 + 321771591.

It is an arithmetic number, because the mean of its divisors is an integer number (321771591).

Almost surely, 2^643543181 is an apocalyptic number.

It is an amenable number.

643543181 is a deficient number, since it is larger than the sum of its proper divisors (1).

643543181 is an equidigital number, since it uses as much as digits as its factorization.

643543181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34560, while the sum is 35.

The square root of 643543181 is about 25368.1528890063. The cubic root of 643543181 is about 863.3612735583.

The spelling of 643543181 in words is "six hundred forty-three million, five hundred forty-three thousand, one hundred eighty-one".