661005516161 has 2 divisors, whose sum is σ = 661005516162. Its totient is φ = 661005516160.

The previous prime is 661005516139. The next prime is 661005516179. The reversal of 661005516161 is 161615500166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 615959698561 + 45045817600 = 784831^2 + 212240^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661005516161 is a prime.

It is not a weakly prime, because it can be changed into another prime (661005516131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330502758080 + 330502758081.

It is an arithmetic number, because the mean of its divisors is an integer number (330502758081).

Almost surely, 2^661005516161 is an apocalyptic number.

It is an amenable number.

661005516161 is a deficient number, since it is larger than the sum of its proper divisors (1).

661005516161 is an equidigital number, since it uses as much as digits as its factorization.

661005516161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32400, while the sum is 38.

The spelling of 661005516161 in words is "six hundred sixty-one billion, five million, five hundred sixteen thousand, one hundred sixty-one".