999968561 has 2 divisors, whose sum is σ = 999968562. Its totient is φ = 999968560.

The previous prime is 999968513. The next prime is 999968573. The reversal of 999968561 is 165869999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 522808225 + 477160336 = 22865^2 + 21844^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999968561 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 999968494 and 999968503.

It is not a weakly prime, because it can be changed into another prime (999968261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499984280 + 499984281.

It is an arithmetic number, because the mean of its divisors is an integer number (499984281).

Almost surely, 2^999968561 is an apocalyptic number.

It is an amenable number.

999968561 is a deficient number, since it is larger than the sum of its proper divisors (1).

999968561 is an equidigital number, since it uses as much as digits as its factorization.

999968561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9447840, while the sum is 62.

The square root of 999968561 is about 31622.2795035399. The cubic root of 999968561 is about 999.9895202235.

The spelling of 999968561 in words is "nine hundred ninety-nine million, nine hundred sixty-eight thousand, five hundred sixty-one".