78665557 has 2 divisors, whose sum is σ = 78665558. Its totient is φ = 78665556.

The previous prime is 78665551. The next prime is 78665611. The reversal of 78665557 is 75556687.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 42497361 + 36168196 = 6519^2 + 6014^2 .

It is a cyclic number.

It is not a de Polignac number, because 78665557 - 2³ = 78665549 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 78665557.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78665551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39332778 + 39332779.

It is an arithmetic number, because the mean of its divisors is an integer number (39332779).

Almost surely, 2^78665557 is an apocalyptic number.

It is an amenable number.

78665557 is a deficient number, since it is larger than the sum of its proper divisors (1).

78665557 is an equidigital number, since it uses as much as digits as its factorization.

78665557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1764000, while the sum is 49.

The square root of 78665557 is about 8869.3605744721. The cubic root of 78665557 is about 428.4776834694.

The spelling of 78665557 in words is "seventy-eight million, six hundred sixty-five thousand, five hundred fifty-seven".