195194917721 has 2 divisors, whose sum is σ = 195194917722. Its totient is φ = 195194917720.

The previous prime is 195194917717. The next prime is 195194917739. The reversal of 195194917721 is 127719491591.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 188365548121 + 6829369600 = 434011^2 + 82640^2 .

It is a cyclic number.

It is not a de Polignac number, because 195194917721 - 2² = 195194917717 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 (195194917741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 97597458860 + 97597458861.

It is an arithmetic number, because the mean of its divisors is an integer number (97597458861).

Almost surely, 2^195194917721 is an apocalyptic number.

It is an amenable number.

195194917721 is a deficient number, since it is larger than the sum of its proper divisors (1).

195194917721 is an equidigital number, since it uses as much as digits as its factorization.

195194917721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1428840, while the sum is 56.

The spelling of 195194917721 in words is "one hundred ninety-five billion, one hundred ninety-four million, nine hundred seventeen thousand, seven hundred twenty-one".