18221237 has 4 divisors (see below), whose sum is σ = 18426060. Its totient is φ = 18016416.

The previous prime is 18221233. The next prime is 18221243. The reversal of 18221237 is 73212281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 73212281 = 2297 ⋅31873.

It can be written as a sum of positive squares in 2 ways, for example, as 2149156 + 16072081 = 1466^2 + 4009^2 .

It is a cyclic number.

It is not a de Polignac number, because 18221237 - 2² = 18221233 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18221233) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 102278 + ... + 102455.

It is an arithmetic number, because the mean of its divisors is an integer number (4606515).

Almost surely, 2^18221237 is an apocalyptic number.

It is an amenable number.

18221237 is a deficient number, since it is larger than the sum of its proper divisors (204823).

18221237 is an equidigital number, since it uses as much as digits as its factorization.

18221237 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 204822.

The product of its digits is 1344, while the sum is 26.

The square root of 18221237 is about 4268.6340906665. The cubic root of 18221237 is about 263.1434831287.

The spelling of 18221237 in words is "eighteen million, two hundred twenty-one thousand, two hundred thirty-seven".