643764851 has 2 divisors, whose sum is σ = 643764852. Its totient is φ = 643764850.

The previous prime is 643764829. The next prime is 643764883. The reversal of 643764851 is 158467346.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643764851 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (643764811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321882425 + 321882426.

It is an arithmetic number, because the mean of its divisors is an integer number (321882426).

Almost surely, 2^643764851 is an apocalyptic number.

643764851 is a deficient number, since it is larger than the sum of its proper divisors (1).

643764851 is an equidigital number, since it uses as much as digits as its factorization.

643764851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 483840, while the sum is 44.

The square root of 643764851 is about 25372.5215735449. The cubic root of 643764851 is about 863.4603911360.

The spelling of 643764851 in words is "six hundred forty-three million, seven hundred sixty-four thousand, eight hundred fifty-one".