66797821 has 2 divisors, whose sum is σ = 66797822. Its totient is φ = 66797820.

The previous prime is 66797779. The next prime is 66797833. The reversal of 66797821 is 12879766.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 46049796 + 20748025 = 6786^2 + 4555^2 .

It is a cyclic number.

It is not a de Polignac number, because 66797821 - 2⁷ = 66797693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66797891) 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, 33398910 + 33398911.

It is an arithmetic number, because the mean of its divisors is an integer number (33398911).

Almost surely, 2^66797821 is an apocalyptic number.

It is an amenable number.

66797821 is a deficient number, since it is larger than the sum of its proper divisors (1).

66797821 is an equidigital number, since it uses as much as digits as its factorization.

66797821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 254016, while the sum is 46.

The square root of 66797821 is about 8172.9933928763. The cubic root of 66797821 is about 405.7458612400.

The spelling of 66797821 in words is "sixty-six million, seven hundred ninety-seven thousand, eight hundred twenty-one".