643846561 has 4 divisors (see below), whose sum is σ = 657545472. Its totient is φ = 630147652.

The previous prime is 643846549. The next prime is 643846571. The reversal of 643846561 is 165648346.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643846561 is a prime.

It is a super-2 number, since 2×643846561² = 829076788223053442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643846501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6849385 + ... + 6849478.

It is an arithmetic number, because the mean of its divisors is an integer number (164386368).

Almost surely, 2^643846561 is an apocalyptic number.

It is an amenable number.

643846561 is a deficient number, since it is larger than the sum of its proper divisors (13698911).

643846561 is a wasteful number, since it uses less digits than its factorization.

643846561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13698910.

The product of its digits is 414720, while the sum is 43.

The square root of 643846561 is about 25374.1317289873. The cubic root of 643846561 is about 863.4969212260.

The spelling of 643846561 in words is "six hundred forty-three million, eight hundred forty-six thousand, five hundred sixty-one".