78105378781 has 2 divisors, whose sum is σ = 78105378782. Its totient is φ = 78105378780.

The previous prime is 78105378763. The next prime is 78105378817. The reversal of 78105378781 is 18787350187.

Together with next prime (78105378817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77539414681 + 565964100 = 278459^2 + 23790^2 .

It is an emirp because it is prime and its reverse (18787350187) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78105378781 - 2¹⁹ = 78104854493 is a prime.

It is a super-2 number, since 2×78105378781² (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 (78105370781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39052689390 + 39052689391.

It is an arithmetic number, because the mean of its divisors is an integer number (39052689391).

Almost surely, 2^78105378781 is an apocalyptic number.

It is an amenable number.

78105378781 is a deficient number, since it is larger than the sum of its proper divisors (1).

78105378781 is an equidigital number, since it uses as much as digits as its factorization.

78105378781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2634240, while the sum is 55.

The spelling of 78105378781 in words is "seventy-eight billion, one hundred five million, three hundred seventy-eight thousand, seven hundred eighty-one".