646143989 has 2 divisors, whose sum is σ = 646143990. Its totient is φ = 646143988.

The previous prime is 646143959. The next prime is 646144027. The reversal of 646143989 is 989341646.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 466128100 + 180015889 = 21590^2 + 13417^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646143989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646143919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323071994 + 323071995.

It is an arithmetic number, because the mean of its divisors is an integer number (323071995).

Almost surely, 2^646143989 is an apocalyptic number.

It is an amenable number.

646143989 is a deficient number, since it is larger than the sum of its proper divisors (1).

646143989 is an equidigital number, since it uses as much as digits as its factorization.

646143989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1119744, while the sum is 50.

The square root of 646143989 is about 25419.3624821709. The cubic root of 646143989 is about 864.5227697108.

The spelling of 646143989 in words is "six hundred forty-six million, one hundred forty-three thousand, nine hundred eighty-nine".