18121421 has 8 divisors (see below), whose sum is σ = 19126080. Its totient is φ = 17121888.

The previous prime is 18121417. The next prime is 18121429. The reversal of 18121421 is 12412181.

18121421 is nontrivially palindromic in base 5.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 18121421 - 2² = 18121417 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18121393 and 18121402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18121429) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7640 + ... + 9726.

It is an arithmetic number, because the mean of its divisors is an integer number (2390760).

Almost surely, 2^18121421 is an apocalyptic number.

It is an amenable number.

18121421 is a deficient number, since it is larger than the sum of its proper divisors (1004659).

18121421 is a wasteful number, since it uses less digits than its factorization.

18121421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2563.

The product of its digits is 128, while the sum is 20.

The square root of 18121421 is about 4256.9262384965. The cubic root of 18121421 is about 262.6621027477.

The spelling of 18121421 in words is "eighteen million, one hundred twenty-one thousand, four hundred twenty-one".