18117421 has 4 divisors (see below), whose sum is σ = 20705632. Its totient is φ = 15529212.

The previous prime is 18117413. The next prime is 18117443. The reversal of 18117421 is 12471181.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12471181 = 2423 ⋅5147.

It is a cyclic number.

It is not a de Polignac number, because 18117421 - 2³ = 18117413 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 (18117401) 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, 1294095 + ... + 1294108.

It is an arithmetic number, because the mean of its divisors is an integer number (5176408).

Almost surely, 2^18117421 is an apocalyptic number.

It is an amenable number.

18117421 is a deficient number, since it is larger than the sum of its proper divisors (2588211).

18117421 is an equidigital number, since it uses as much as digits as its factorization.

18117421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2588210.

The product of its digits is 448, while the sum is 25.

The square root of 18117421 is about 4256.4563900033. The cubic root of 18117421 is about 262.6427752397.

The spelling of 18117421 in words is "eighteen million, one hundred seventeen thousand, four hundred twenty-one".