18237421 has 2 divisors, whose sum is σ = 18237422. Its totient is φ = 18237420.

The previous prime is 18237419. The next prime is 18237449. The reversal of 18237421 is 12473281.

It is an a-pointer prime, because the next prime (18237449) can be obtained adding 18237421 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14356521 + 3880900 = 3789^2 + 1970^2 .

It is an emirp because it is prime and its reverse (12473281) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18237421 - 2¹ = 18237419 is a prime.

Together with 18237419, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18237421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18237221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9118710 + 9118711.

It is an arithmetic number, because the mean of its divisors is an integer number (9118711).

Almost surely, 2^18237421 is an apocalyptic number.

It is an amenable number.

18237421 is a deficient number, since it is larger than the sum of its proper divisors (1).

18237421 is an equidigital number, since it uses as much as digits as its factorization.

18237421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 28.

The square root of 18237421 is about 4270.5293582880. The cubic root of 18237421 is about 263.2213675939.

The spelling of 18237421 in words is "eighteen million, two hundred thirty-seven thousand, four hundred twenty-one".