18711521 has 2 divisors, whose sum is σ = 18711522. Its totient is φ = 18711520.

The previous prime is 18711503. The next prime is 18711527. The reversal of 18711521 is 12511781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16851025 + 1860496 = 4105^2 + 1364^2 .

It is a cyclic number.

It is not a de Polignac number, because 18711521 - 2¹⁴ = 18695137 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18711527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9355760 + 9355761.

It is an arithmetic number, because the mean of its divisors is an integer number (9355761).

Almost surely, 2^18711521 is an apocalyptic number.

It is an amenable number.

18711521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18711521 is an equidigital number, since it uses as much as digits as its factorization.

18711521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 560, while the sum is 26.

The square root of 18711521 is about 4325.6815647942. The cubic root of 18711521 is about 265.4827843280.

The spelling of 18711521 in words is "eighteen million, seven hundred eleven thousand, five hundred twenty-one".