18051221 has 8 divisors (see below), whose sum is σ = 18477504. Its totient is φ = 17629920.

The previous prime is 18051211. The next prime is 18051223. The reversal of 18051221 is 12215081.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18051221 - 2¹⁴ = 18034837 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18051193 and 18051202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18051223) 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 7 ways as a sum of consecutive naturals, for example, 6656 + ... + 8966.

It is an arithmetic number, because the mean of its divisors is an integer number (2309688).

Almost surely, 2^18051221 is an apocalyptic number.

It is an amenable number.

18051221 is a deficient number, since it is larger than the sum of its proper divisors (426283).

18051221 is a wasteful number, since it uses less digits than its factorization.

18051221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2491.

The product of its (nonzero) digits is 160, while the sum is 20.

The square root of 18051221 is about 4248.6728516091. The cubic root of 18051221 is about 262.3224910266.

The spelling of 18051221 in words is "eighteen million, fifty-one thousand, two hundred twenty-one".