78318121891 has 2 divisors, whose sum is σ = 78318121892. Its totient is φ = 78318121890.

The previous prime is 78318121879. The next prime is 78318121907. The reversal of 78318121891 is 19812181387.

It is a weak prime.

It is an emirp because it is prime and its reverse (19812181387) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78318121891 - 2⁹ = 78318121379 is a prime.

It is a super-2 number, since 2×78318121891² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78318121291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39159060945 + 39159060946.

It is an arithmetic number, because the mean of its divisors is an integer number (39159060946).

Almost surely, 2^78318121891 is an apocalyptic number.

78318121891 is a deficient number, since it is larger than the sum of its proper divisors (1).

78318121891 is an equidigital number, since it uses as much as digits as its factorization.

78318121891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 49.

The spelling of 78318121891 in words is "seventy-eight billion, three hundred eighteen million, one hundred twenty-one thousand, eight hundred ninety-one".