643165381 has 2 divisors, whose sum is σ = 643165382. Its totient is φ = 643165380.

The previous prime is 643165379. The next prime is 643165417. The reversal of 643165381 is 183561346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 628304356 + 14861025 = 25066^2 + 3855^2 .

It is a cyclic number.

It is not a de Polignac number, because 643165381 - 2¹ = 643165379 is a prime.

It is a super-2 number, since 2×643165381² = 827323414633750322, which contains 22 as substring.

Together with 643165379, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 643165381.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643165321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321582690 + 321582691.

It is an arithmetic number, because the mean of its divisors is an integer number (321582691).

Almost surely, 2^643165381 is an apocalyptic number.

It is an amenable number.

643165381 is a deficient number, since it is larger than the sum of its proper divisors (1).

643165381 is an equidigital number, since it uses as much as digits as its factorization.

643165381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 51840, while the sum is 37.

The square root of 643165381 is about 25360.7054515445. The cubic root of 643165381 is about 863.1922915078.

The spelling of 643165381 in words is "six hundred forty-three million, one hundred sixty-five thousand, three hundred eighty-one".