18431521 has 2 divisors, whose sum is σ = 18431522. Its totient is φ = 18431520.

The previous prime is 18431503. The next prime is 18431527. The reversal of 18431521 is 12513481.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17969121 + 462400 = 4239^2 + 680^2 .

It is an emirp because it is prime and its reverse (12513481) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18431521 - 2¹⁵ = 18398753 is a prime.

It is not a weakly prime, because it can be changed into another prime (18431527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9215760 + 9215761.

It is an arithmetic number, because the mean of its divisors is an integer number (9215761).

Almost surely, 2^18431521 is an apocalyptic number.

It is an amenable number.

18431521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18431521 is an equidigital number, since it uses as much as digits as its factorization.

18431521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 960, while the sum is 25.

The square root of 18431521 is about 4293.1947311996. The cubic root of 18431521 is about 264.1518916638.

It can be divided in two parts, 1843 and 1521, that added together give a square (3364 = 58²).

The spelling of 18431521 in words is "eighteen million, four hundred thirty-one thousand, five hundred twenty-one".