18643221 has 12 divisors (see below), whose sum is σ = 27071148. Its totient is φ = 12363264.

The previous prime is 18643217. The next prime is 18643249. The reversal of 18643221 is 12234681.

18643221 is a `hidden beast` number, since 18 + 643 + 2 + 2 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 2842596 + 15800625 = 1686^2 + 3975^2 .

It is not a de Polignac number, because 18643221 - 2² = 18643217 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18643021) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3630 + ... + 7103.

It is an arithmetic number, because the mean of its divisors is an integer number (2255929).

Almost surely, 2^18643221 is an apocalyptic number.

It is an amenable number.

18643221 is a deficient number, since it is larger than the sum of its proper divisors (8427927).

18643221 is a wasteful number, since it uses less digits than its factorization.

18643221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10932 (or 10929 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 18643221 is about 4317.7796377305. The cubic root of 18643221 is about 265.1593725087.

The spelling of 18643221 in words is "eighteen million, six hundred forty-three thousand, two hundred twenty-one".