78158745531781 has 2 divisors, whose sum is σ = 78158745531782. Its totient is φ = 78158745531780.

The previous prime is 78158745531721. The next prime is 78158745531793. The reversal of 78158745531781 is 18713554785187.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70742061288900 + 7416684242881 = 8410830^2 + 2723359^2 .

It is a cyclic number.

It is not a de Polignac number, because 78158745531781 - 2⁷ = 78158745531653 is a prime.

It is a super-2 number, since 2×78158745531781² (a number of 29 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 78158745531781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78158745531721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39079372765890 + 39079372765891.

It is an arithmetic number, because the mean of its divisors is an integer number (39079372765891).

Almost surely, 2^{78158745531781} is an apocalyptic number.

It is an amenable number.

78158745531781 is a deficient number, since it is larger than the sum of its proper divisors (1).

78158745531781 is an equidigital number, since it uses as much as digits as its factorization.

78158745531781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 263424000, while the sum is 70.

The spelling of 78158745531781 in words is "seventy-eight trillion, one hundred fifty-eight billion, seven hundred forty-five million, five hundred thirty-one thousand, seven hundred eighty-one".