78378668161 has 2 divisors, whose sum is σ = 78378668162. Its totient is φ = 78378668160.

The previous prime is 78378668107. The next prime is 78378668189. The reversal of 78378668161 is 16186687387.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 75347505025 + 3031163136 = 274495^2 + 55056^2 .

It is a cyclic number.

It is not a de Polignac number, because 78378668161 - 2⁹ = 78378667649 is a prime.

It is a super-2 number, since 2×78378668161² (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 78378668161.

It is not a weakly prime, because it can be changed into another prime (78378668101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39189334080 + 39189334081.

It is an arithmetic number, because the mean of its divisors is an integer number (39189334081).

Almost surely, 2^78378668161 is an apocalyptic number.

It is an amenable number.

78378668161 is a deficient number, since it is larger than the sum of its proper divisors (1).

78378668161 is an equidigital number, since it uses as much as digits as its factorization.

78378668161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16257024, while the sum is 61.

The spelling of 78378668161 in words is "seventy-eight billion, three hundred seventy-eight million, six hundred sixty-eight thousand, one hundred sixty-one".