78195345821 has 2 divisors, whose sum is σ = 78195345822. Its totient is φ = 78195345820.

The previous prime is 78195345817. The next prime is 78195345827. The reversal of 78195345821 is 12854359187.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77434192900 + 761152921 = 278270^2 + 27589^2 .

It is a cyclic number.

It is not a de Polignac number, because 78195345821 - 2² = 78195345817 is a prime.

It is a super-2 number, since 2×78195345821² (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 (78195345827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39097672910 + 39097672911.

It is an arithmetic number, because the mean of its divisors is an integer number (39097672911).

Almost surely, 2^78195345821 is an apocalyptic number.

It is an amenable number.

78195345821 is a deficient number, since it is larger than the sum of its proper divisors (1).

78195345821 is an equidigital number, since it uses as much as digits as its factorization.

78195345821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2419200, while the sum is 53.

The spelling of 78195345821 in words is "seventy-eight billion, one hundred ninety-five million, three hundred forty-five thousand, eight hundred twenty-one".