646863851 has 2 divisors, whose sum is σ = 646863852. Its totient is φ = 646863850.

The previous prime is 646863829. The next prime is 646863853. The reversal of 646863851 is 158368646.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646863851 is a prime.

Together with 646863853, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 646863796 and 646863805.

It is not a weakly prime, because it can be changed into another prime (646863853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323431925 + 323431926.

It is an arithmetic number, because the mean of its divisors is an integer number (323431926).

Almost surely, 2^646863851 is an apocalyptic number.

646863851 is a deficient number, since it is larger than the sum of its proper divisors (1).

646863851 is an equidigital number, since it uses as much as digits as its factorization.

646863851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 829440, while the sum is 47.

The square root of 646863851 is about 25433.5182583928. The cubic root of 646863851 is about 864.8437023670.

The spelling of 646863851 in words is "six hundred forty-six million, eight hundred sixty-three thousand, eight hundred fifty-one".