643293779581 has 2 divisors, whose sum is σ = 643293779582. Its totient is φ = 643293779580.

The previous prime is 643293779563. The next prime is 643293779647. The reversal of 643293779581 is 185977392346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 582428448900 + 60865330681 = 763170^2 + 246709^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643293779581 is a prime.

It is a super-2 number, since 2×643293779581² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643293779501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321646889790 + 321646889791.

It is an arithmetic number, because the mean of its divisors is an integer number (321646889791).

Almost surely, 2^643293779581 is an apocalyptic number.

It is an amenable number.

643293779581 is a deficient number, since it is larger than the sum of its proper divisors (1).

643293779581 is an equidigital number, since it uses as much as digits as its factorization.

643293779581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 68584320, while the sum is 64.

The spelling of 643293779581 in words is "six hundred forty-three billion, two hundred ninety-three million, seven hundred seventy-nine thousand, five hundred eighty-one".