18735221 has 2 divisors, whose sum is σ = 18735222. Its totient is φ = 18735220.

The previous prime is 18735217. The next prime is 18735239. The reversal of 18735221 is 12253781.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16443025 + 2292196 = 4055^2 + 1514^2 .

It is a cyclic number.

It is not a de Polignac number, because 18735221 - 2² = 18735217 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18735251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9367610 + 9367611.

It is an arithmetic number, because the mean of its divisors is an integer number (9367611).

Almost surely, 2^18735221 is an apocalyptic number.

It is an amenable number.

18735221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18735221 is an equidigital number, since it uses as much as digits as its factorization.

18735221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3360, while the sum is 29.

The square root of 18735221 is about 4328.4201505861. The cubic root of 18735221 is about 265.5948238107.

The spelling of 18735221 in words is "eighteen million, seven hundred thirty-five thousand, two hundred twenty-one".