78238907521 has 2 divisors, whose sum is σ = 78238907522. Its totient is φ = 78238907520.

The previous prime is 78238907497. The next prime is 78238907531. The reversal of 78238907521 is 12570983287.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73731799296 + 4507108225 = 271536^2 + 67135^2 .

It is a cyclic number.

It is not a de Polignac number, because 78238907521 - 2⁷ = 78238907393 is a prime.

It is a super-2 number, since 2×78238907521² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78238907531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39119453760 + 39119453761.

It is an arithmetic number, because the mean of its divisors is an integer number (39119453761).

Almost surely, 2^78238907521 is an apocalyptic number.

It is an amenable number.

78238907521 is a deficient number, since it is larger than the sum of its proper divisors (1).

78238907521 is an equidigital number, since it uses as much as digits as its factorization.

78238907521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1693440, while the sum is 52.

The spelling of 78238907521 in words is "seventy-eight billion, two hundred thirty-eight million, nine hundred seven thousand, five hundred twenty-one".