18218421 has 24 divisors (see below), whose sum is σ = 29259776. Its totient is φ = 10847520.

The previous prime is 18218413. The next prime is 18218423. The reversal of 18218421 is 12481281.

It is not a de Polignac number, because 18218421 - 2³ = 18218413 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18218423) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1116 + ... + 6138.

Almost surely, 2^18218421 is an apocalyptic number.

It is an amenable number.

18218421 is a deficient number, since it is larger than the sum of its proper divisors (11041355).

18218421 is a wasteful number, since it uses less digits than its factorization.

18218421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5073 (or 5070 counting only the distinct ones).

The product of its digits is 1024, while the sum is 27.

The square root of 18218421 is about 4268.3042300192. The cubic root of 18218421 is about 263.1299265989.

The spelling of 18218421 in words is "eighteen million, two hundred eighteen thousand, four hundred twenty-one".