18207521 has 2 divisors, whose sum is σ = 18207522. Its totient is φ = 18207520.

The previous prime is 18207499. The next prime is 18207547. The reversal of 18207521 is 12570281.

It is an a-pointer prime, because the next prime (18207547) can be obtained adding 18207521 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16289296 + 1918225 = 4036^2 + 1385^2 .

It is an emirp because it is prime and its reverse (12570281) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18207521 - 2¹⁰ = 18206497 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18207551) 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, 9103760 + 9103761.

It is an arithmetic number, because the mean of its divisors is an integer number (9103761).

Almost surely, 2^18207521 is an apocalyptic number.

It is an amenable number.

18207521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18207521 is an equidigital number, since it uses as much as digits as its factorization.

18207521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 18207521 is about 4267.0271852895. The cubic root of 18207521 is about 263.0774396429.

The spelling of 18207521 in words is "eighteen million, two hundred seven thousand, five hundred twenty-one".