9866561 has 2 divisors, whose sum is σ = 9866562. Its totient is φ = 9866560.

The previous prime is 9866557. The next prime is 9866573. The reversal of 9866561 is 1656689.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9265936 + 600625 = 3044^2 + 775^2 .

It is an emirp because it is prime and its reverse (1656689) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9866561 - 2² = 9866557 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 (9866501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4933280 + 4933281.

It is an arithmetic number, because the mean of its divisors is an integer number (4933281).

Almost surely, 2^9866561 is an apocalyptic number.

It is an amenable number.

9866561 is a deficient number, since it is larger than the sum of its proper divisors (1).

9866561 is an equidigital number, since it uses as much as digits as its factorization.

9866561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 77760, while the sum is 41.

The square root of 9866561 is about 3141.1082439165. The cubic root of 9866561 is about 214.4808893307.

The spelling of 9866561 in words is "nine million, eight hundred sixty-six thousand, five hundred sixty-one".