78139612726421 has 2 divisors, whose sum is σ = 78139612726422. Its totient is φ = 78139612726420.

The previous prime is 78139612726397. The next prime is 78139612726447. The reversal of 78139612726421 is 12462721693187.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77626936678225 + 512676048196 = 8810615^2 + 716014^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78139612726421 is a prime.

It is a super-2 number, since 2×78139612726421² (a number of 29 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78139612726621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39069806363210 + 39069806363211.

It is an arithmetic number, because the mean of its divisors is an integer number (39069806363211).

Almost surely, 2^{78139612726421} is an apocalyptic number.

It is an amenable number.

78139612726421 is a deficient number, since it is larger than the sum of its proper divisors (1).

78139612726421 is an equidigital number, since it uses as much as digits as its factorization.

78139612726421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12192768, while the sum is 59.

The spelling of 78139612726421 in words is "seventy-eight trillion, one hundred thirty-nine billion, six hundred twelve million, seven hundred twenty-six thousand, four hundred twenty-one".