18656641 has 4 divisors (see below), whose sum is σ = 18665284. Its totient is φ = 18648000.

The previous prime is 18656629. The next prime is 18656647. The reversal of 18656641 is 14665681.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 14665681 = 61 ⋅240421.

It can be written as a sum of positive squares in 2 ways, for example, as 3610000 + 15046641 = 1900^2 + 3879^2 .

It is a cyclic number.

It is not a de Polignac number, because 18656641 - 2⁵ = 18656609 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 18656641.

It is not an unprimeable number, because it can be changed into a prime (18656647) 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, 1981 + ... + 6421.

It is an arithmetic number, because the mean of its divisors is an integer number (4666321).

Almost surely, 2^18656641 is an apocalyptic number.

It is an amenable number.

18656641 is a deficient number, since it is larger than the sum of its proper divisors (8643).

18656641 is an equidigital number, since it uses as much as digits as its factorization.

18656641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8642.

The product of its digits is 34560, while the sum is 37.

The square root of 18656641 is about 4319.3333976437. Note that the first 4 decimals coincide. The cubic root of 18656641 is about 265.2229807106. Note that the first 3 decimals are identical.

The spelling of 18656641 in words is "eighteen million, six hundred fifty-six thousand, six hundred forty-one".