18221551 has 8 divisors (see below), whose sum is σ = 19627520. Its totient is φ = 16860312.

The previous prime is 18221549. The next prime is 18221561. The reversal of 18221551 is 15512281.

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 18221551 - 2¹ = 18221549 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 (18221561) 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 in 7 ways as a sum of consecutive naturals, for example, 10335 + ... + 11968.

It is an arithmetic number, because the mean of its divisors is an integer number (2453440).

Almost surely, 2^18221551 is an apocalyptic number.

18221551 is a deficient number, since it is larger than the sum of its proper divisors (1405969).

18221551 is a wasteful number, since it uses less digits than its factorization.

18221551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22365.

The product of its digits is 800, while the sum is 25.

The square root of 18221551 is about 4268.6708704233. The cubic root of 18221551 is about 263.1449946722.

The spelling of 18221551 in words is "eighteen million, two hundred twenty-one thousand, five hundred fifty-one".