78318164021 has 2 divisors, whose sum is σ = 78318164022. Its totient is φ = 78318164020.

The previous prime is 78318164017. The next prime is 78318164053. The reversal of 78318164021 is 12046181387.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64561219921 + 13756944100 = 254089^2 + 117290^2 .

It is an emirp because it is prime and its reverse (12046181387) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78318164021 - 2² = 78318164017 is a prime.

It is a super-2 number, since 2×78318164021² (a number of 23 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 78318164021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78318164011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39159082010 + 39159082011.

It is an arithmetic number, because the mean of its divisors is an integer number (39159082011).

Almost surely, 2^78318164021 is an apocalyptic number.

It is an amenable number.

78318164021 is a deficient number, since it is larger than the sum of its proper divisors (1).

78318164021 is an equidigital number, since it uses as much as digits as its factorization.

78318164021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64512, while the sum is 41.

The spelling of 78318164021 in words is "seventy-eight billion, three hundred eighteen million, one hundred sixty-four thousand, twenty-one".