18551 has 4 divisors (see below), whose sum is σ = 19992. Its totient is φ = 17112.

The previous prime is 18541. The next prime is 18553. The reversal of 18551 is 15581.

18551 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18551 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 (18553) 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, 701 + ... + 726.

It is an arithmetic number, because the mean of its divisors is an integer number (4998).

2¹⁸⁵⁵¹ is an apocalyptic number.

18551 is a deficient number, since it is larger than the sum of its proper divisors (1441).

18551 is a wasteful number, since it uses less digits than its factorization.

18551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1440.

The product of its digits is 200, while the sum is 20.

The square root of 18551 is about 136.2020557848. The cubic root of 18551 is about 26.4721435058.

The spelling of 18551 in words is "eighteen thousand, five hundred fifty-one".