20166521 has 2 divisors, whose sum is σ = 20166522. Its totient is φ = 20166520.

The previous prime is 20166511. The next prime is 20166529. The reversal of 20166521 is 12566102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15054400 + 5112121 = 3880^2 + 2261^2 .

It is a cyclic number.

It is not a de Polignac number, because 20166521 - 2¹⁸ = 19904377 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20166529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10083260 + 10083261.

It is an arithmetic number, because the mean of its divisors is an integer number (10083261).

Almost surely, 2^20166521 is an apocalyptic number.

It is an amenable number.

20166521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20166521 is an equidigital number, since it uses as much as digits as its factorization.

20166521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 20166521 is about 4490.7149764820. The cubic root of 20166521 is about 272.1930263720.

The spelling of 20166521 in words is "twenty million, one hundred sixty-six thousand, five hundred twenty-one".