18221511 has 48 divisors (see below), whose sum is σ = 31256064. Its totient is φ = 9240000.

The previous prime is 18221509. The next prime is 18221519. The reversal of 18221511 is 11512281.

It is not a de Polignac number, because 18221511 - 2¹ = 18221509 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18221519) 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 47 ways as a sum of consecutive naturals, for example, 180361 + ... + 180461.

It is an arithmetic number, because the mean of its divisors is an integer number (651168).

Almost surely, 2^18221511 is an apocalyptic number.

18221511 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18221511 is a deficient number, since it is larger than the sum of its proper divisors (13034553).

18221511 is a wasteful number, since it uses less digits than its factorization.

18221511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 204 (or 193 counting only the distinct ones).

The product of its digits is 160, while the sum is 21.

The square root of 18221511 is about 4268.6661851215. Note that the first 3 decimals coincide. The cubic root of 18221511 is about 263.1448021199.

Adding to 18221511 its reverse (11512281), we get a palindrome (29733792).

It can be divided in two parts, 1822 and 1511, that added together give a palindrome (3333).

The spelling of 18221511 in words is "eighteen million, two hundred twenty-one thousand, five hundred eleven".