78117215851 has 2 divisors, whose sum is σ = 78117215852. Its totient is φ = 78117215850.

The previous prime is 78117215807. The next prime is 78117215941. The reversal of 78117215851 is 15851271187.

It is a weak prime.

It is an emirp because it is prime and its reverse (15851271187) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78117215851 - 2⁷ = 78117215723 is a prime.

It is a super-2 number, since 2×78117215851² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78117215651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39058607925 + 39058607926.

It is an arithmetic number, because the mean of its divisors is an integer number (39058607926).

Almost surely, 2^78117215851 is an apocalyptic number.

78117215851 is a deficient number, since it is larger than the sum of its proper divisors (1).

78117215851 is an equidigital number, since it uses as much as digits as its factorization.

78117215851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 156800, while the sum is 46.

The spelling of 78117215851 in words is "seventy-eight billion, one hundred seventeen million, two hundred fifteen thousand, eight hundred fifty-one".