18365521 has 2 divisors, whose sum is σ = 18365522. Its totient is φ = 18365520.

The previous prime is 18365513. The next prime is 18365539. The reversal of 18365521 is 12556381.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11316496 + 7049025 = 3364^2 + 2655^2 .

It is an emirp because it is prime and its reverse (12556381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18365521 - 2³ = 18365513 is a prime.

It is not a weakly prime, because it can be changed into another prime (18368521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9182760 + 9182761.

It is an arithmetic number, because the mean of its divisors is an integer number (9182761).

Almost surely, 2^18365521 is an apocalyptic number.

It is an amenable number.

18365521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18365521 is an equidigital number, since it uses as much as digits as its factorization.

18365521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7200, while the sum is 31.

The square root of 18365521 is about 4285.5012542292. The cubic root of 18365521 is about 263.8362209219.

It can be divided in two parts, 18 and 365521, that multiplied together give a triangular number (6579378 = T₃₆₂₇).

The spelling of 18365521 in words is "eighteen million, three hundred sixty-five thousand, five hundred twenty-one".