18018421 has 4 divisors (see below), whose sum is σ = 18139500. Its totient is φ = 17897344.

The previous prime is 18018401. The next prime is 18018433. The reversal of 18018421 is 12481081.

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

It can be written as a sum of positive squares in 2 ways, for example, as 8346321 + 9672100 = 2889^2 + 3110^2 .

It is a cyclic number.

It is not a de Polignac number, because 18018421 - 2⁷ = 18018293 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 (18018401) 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, 60316 + ... + 60613.

It is an arithmetic number, because the mean of its divisors is an integer number (4534875).

Almost surely, 2^18018421 is an apocalyptic number.

It is an amenable number.

18018421 is a deficient number, since it is larger than the sum of its proper divisors (121079).

18018421 is a wasteful number, since it uses less digits than its factorization.

18018421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121078.

The product of its (nonzero) digits is 512, while the sum is 25.

The square root of 18018421 is about 4244.8110676448. The cubic root of 18018421 is about 262.1635101949.

The spelling of 18018421 in words is "eighteen million, eighteen thousand, four hundred twenty-one".