643561111 has 4 divisors (see below), whose sum is σ = 652625424. Its totient is φ = 634496800.

The previous prime is 643561073. The next prime is 643561123. The reversal of 643561111 is 111165346.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643561111 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643561111.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643561151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4532050 + ... + 4532191.

It is an arithmetic number, because the mean of its divisors is an integer number (163156356).

Almost surely, 2^643561111 is an apocalyptic number.

643561111 is a deficient number, since it is larger than the sum of its proper divisors (9064313).

643561111 is an equidigital number, since it uses as much as digits as its factorization.

643561111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9064312.

The product of its digits is 2160, while the sum is 28.

The square root of 643561111 is about 25368.5062823967. The cubic root of 643561111 is about 863.3692916288.

The spelling of 643561111 in words is "six hundred forty-three million, five hundred sixty-one thousand, one hundred eleven".