18521231 has 2 divisors, whose sum is σ = 18521232. Its totient is φ = 18521230.

The previous prime is 18521213. The next prime is 18521267. The reversal of 18521231 is 13212581.

It is a happy number.

Together with previous prime (18521213) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18521231 is a prime.

It is a super-2 number, since 2×18521231² = 686071995510722, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 18521197 and 18521206.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18521281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9260615 + 9260616.

It is an arithmetic number, because the mean of its divisors is an integer number (9260616).

Almost surely, 2^18521231 is an apocalyptic number.

18521231 is a deficient number, since it is larger than the sum of its proper divisors (1).

18521231 is an equidigital number, since it uses as much as digits as its factorization.

18521231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 480, while the sum is 23.

The square root of 18521231 is about 4303.6299794476. The cubic root of 18521231 is about 264.5797587519.

The spelling of 18521231 in words is "eighteen million, five hundred twenty-one thousand, two hundred thirty-one".