66778417 has 2 divisors, whose sum is σ = 66778418. Its totient is φ = 66778416.

The previous prime is 66778351. The next prime is 66778421. The reversal of 66778417 is 71487766.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 34527376 + 32251041 = 5876^2 + 5679^2 .

It is a cyclic number.

It is not a de Polignac number, because 66778417 - 2⁷ = 66778289 is a prime.

It is not a weakly prime, because it can be changed into another prime (66778477) 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, 33389208 + 33389209.

It is an arithmetic number, because the mean of its divisors is an integer number (33389209).

Almost surely, 2^66778417 is an apocalyptic number.

It is an amenable number.

66778417 is a deficient number, since it is larger than the sum of its proper divisors (1).

66778417 is an equidigital number, since it uses as much as digits as its factorization.

66778417 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 395136, while the sum is 46.

The square root of 66778417 is about 8171.8062262880. The cubic root of 66778417 is about 405.7065692638.

The spelling of 66778417 in words is "sixty-six million, seven hundred seventy-eight thousand, four hundred seventeen".