81768185861 has 2 divisors, whose sum is σ = 81768185862. Its totient is φ = 81768185860.

The previous prime is 81768185809. The next prime is 81768185867. The reversal of 81768185861 is 16858186718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62605044100 + 19163141761 = 250210^2 + 138431^2 .

It is a cyclic number.

It is not a de Polignac number, because 81768185861 - 2⁶ = 81768185797 is a prime.

It is a super-2 number, since 2×81768185861² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81768185861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81768185867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40884092930 + 40884092931.

It is an arithmetic number, because the mean of its divisors is an integer number (40884092931).

Almost surely, 2^81768185861 is an apocalyptic number.

It is an amenable number.

81768185861 is a deficient number, since it is larger than the sum of its proper divisors (1).

81768185861 is an equidigital number, since it uses as much as digits as its factorization.

81768185861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5160960, while the sum is 59.

The spelling of 81768185861 in words is "eighty-one billion, seven hundred sixty-eight million, one hundred eighty-five thousand, eight hundred sixty-one".