18206521 has 2 divisors, whose sum is σ = 18206522. Its totient is φ = 18206520.

The previous prime is 18206509. The next prime is 18206527. The reversal of 18206521 is 12560281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15681600 + 2524921 = 3960^2 + 1589^2 .

It is an emirp because it is prime and its reverse (12560281) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18206521 - 2²¹ = 16109369 is a prime.

It is not a weakly prime, because it can be changed into another prime (18206527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9103260 + 9103261.

It is an arithmetic number, because the mean of its divisors is an integer number (9103261).

Almost surely, 2^18206521 is an apocalyptic number.

It is an amenable number.

18206521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18206521 is an equidigital number, since it uses as much as digits as its factorization.

18206521 is an evil number, because the sum of its binary digits is even.

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

The square root of 18206521 is about 4266.9100060817. The cubic root of 18206521 is about 263.0726232769.

The spelling of 18206521 in words is "eighteen million, two hundred six thousand, five hundred twenty-one".