823220561 has 2 divisors, whose sum is σ = 823220562. Its totient is φ = 823220560.

The previous prime is 823220537. The next prime is 823220617. The reversal of 823220561 is 165022328.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 710542336 + 112678225 = 26656^2 + 10615^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-823220561 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 (823220261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 411610280 + 411610281.

It is an arithmetic number, because the mean of its divisors is an integer number (411610281).

Almost surely, 2^823220561 is an apocalyptic number.

It is an amenable number.

823220561 is a deficient number, since it is larger than the sum of its proper divisors (1).

823220561 is an equidigital number, since it uses as much as digits as its factorization.

823220561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 823220561 is about 28691.8204546174. The cubic root of 823220561 is about 937.2139328907.

Adding to 823220561 its reverse (165022328), we get a palindrome (988242889).

The spelling of 823220561 in words is "eight hundred twenty-three million, two hundred twenty thousand, five hundred sixty-one".