661621353161 has 2 divisors, whose sum is σ = 661621353162. Its totient is φ = 661621353160.

The previous prime is 661621353131. The next prime is 661621353163. The reversal of 661621353161 is 161353126166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 659985636025 + 1635717136 = 812395^2 + 40444^2 .

It is a cyclic number.

It is not a de Polignac number, because 661621353161 - 2¹⁸ = 661621091017 is a prime.

Together with 661621353163, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (661621353163) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330810676580 + 330810676581.

It is an arithmetic number, because the mean of its divisors is an integer number (330810676581).

Almost surely, 2^661621353161 is an apocalyptic number.

It is an amenable number.

661621353161 is a deficient number, since it is larger than the sum of its proper divisors (1).

661621353161 is an equidigital number, since it uses as much as digits as its factorization.

661621353161 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 116640, while the sum is 41.

The spelling of 661621353161 in words is "six hundred sixty-one billion, six hundred twenty-one million, three hundred fifty-three thousand, one hundred sixty-one".