19961289221 has 2 divisors, whose sum is σ = 19961289222. Its totient is φ = 19961289220.

The previous prime is 19961289203. The next prime is 19961289259. The reversal of 19961289221 is 12298216991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15799233025 + 4162056196 = 125695^2 + 64514^2 .

It is a cyclic number.

It is not a de Polignac number, because 19961289221 - 2¹⁰ = 19961288197 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19961289221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19961289121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9980644610 + 9980644611.

It is an arithmetic number, because the mean of its divisors is an integer number (9980644611).

Almost surely, 2^19961289221 is an apocalyptic number.

It is an amenable number.

19961289221 is a deficient number, since it is larger than the sum of its proper divisors (1).

19961289221 is an equidigital number, since it uses as much as digits as its factorization.

19961289221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 279936, while the sum is 50.

The spelling of 19961289221 in words is "nineteen billion, nine hundred sixty-one million, two hundred eighty-nine thousand, two hundred twenty-one".