78368191981 has 2 divisors, whose sum is σ = 78368191982. Its totient is φ = 78368191980.

The previous prime is 78368191973. The next prime is 78368192017. The reversal of 78368191981 is 18919186387.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 66697711081 + 11670480900 = 258259^2 + 108030^2 .

It is a cyclic number.

It is not a de Polignac number, because 78368191981 - 2³ = 78368191973 is a prime.

It is a super-2 number, since 2×78368191981² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78368191961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39184095990 + 39184095991.

It is an arithmetic number, because the mean of its divisors is an integer number (39184095991).

Almost surely, 2^78368191981 is an apocalyptic number.

It is an amenable number.

78368191981 is a deficient number, since it is larger than the sum of its proper divisors (1).

78368191981 is an equidigital number, since it uses as much as digits as its factorization.

78368191981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5225472, while the sum is 61.

The spelling of 78368191981 in words is "seventy-eight billion, three hundred sixty-eight million, one hundred ninety-one thousand, nine hundred eighty-one".