66278813 has 2 divisors, whose sum is σ = 66278814. Its totient is φ = 66278812.

The previous prime is 66278791. The next prime is 66278831. The reversal of 66278813 is 31887266.

It is a happy number.

Together with next prime (66278831) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 36445369 + 29833444 = 6037^2 + 5462^2 .

It is a cyclic number.

It is not a de Polignac number, because 66278813 - 2⁸ = 66278557 is a prime.

It is a Sophie Germain prime.

It is a Chen 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 (66271813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33139406 + 33139407.

It is an arithmetic number, because the mean of its divisors is an integer number (33139407).

Almost surely, 2^66278813 is an apocalyptic number.

It is an amenable number.

66278813 is a deficient number, since it is larger than the sum of its proper divisors (1).

66278813 is an equidigital number, since it uses as much as digits as its factorization.

66278813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 96768, while the sum is 41.

The square root of 66278813 is about 8141.1800741662. The cubic root of 66278813 is about 404.6922683944.

The spelling of 66278813 in words is "sixty-six million, two hundred seventy-eight thousand, eight hundred thirteen".