561166721 has 2 divisors, whose sum is σ = 561166722. Its totient is φ = 561166720.

The previous prime is 561166709. The next prime is 561166751. The reversal of 561166721 is 127661165.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 500014321 + 61152400 = 22361^2 + 7820^2 .

It is a cyclic number.

It is not a de Polignac number, because 561166721 - 2²² = 556972417 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (561166751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 280583360 + 280583361.

It is an arithmetic number, because the mean of its divisors is an integer number (280583361).

Almost surely, 2^561166721 is an apocalyptic number.

It is an amenable number.

561166721 is a deficient number, since it is larger than the sum of its proper divisors (1).

561166721 is an equidigital number, since it uses as much as digits as its factorization.

561166721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15120, while the sum is 35.

The square root of 561166721 is about 23688.9577862767. The cubic root of 561166721 is about 824.8290902773.

The spelling of 561166721 in words is "five hundred sixty-one million, one hundred sixty-six thousand, seven hundred twenty-one".