643666351 has 2 divisors, whose sum is σ = 643666352. Its totient is φ = 643666350.

The previous prime is 643666343. The next prime is 643666367. The reversal of 643666351 is 153666346.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643666351 - 2³ = 643666343 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643666301) 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, 321833175 + 321833176.

It is an arithmetic number, because the mean of its divisors is an integer number (321833176).

Almost surely, 2^643666351 is an apocalyptic number.

643666351 is a deficient number, since it is larger than the sum of its proper divisors (1).

643666351 is an equidigital number, since it uses as much as digits as its factorization.

643666351 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 233280, while the sum is 40.

The square root of 643666351 is about 25370.5804230018. The cubic root of 643666351 is about 863.4163506314.

The spelling of 643666351 in words is "six hundred forty-three million, six hundred sixty-six thousand, three hundred fifty-one".