66727781 has 2 divisors, whose sum is σ = 66727782. Its totient is φ = 66727780.

The previous prime is 66727769. The next prime is 66727783. The reversal of 66727781 is 18772766.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 59752900 + 6974881 = 7730^2 + 2641^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66727781 is a prime.

It is a super-2 number, since 2×66727781² = 8905193514367922, which contains 22 as substring.

Together with 66727783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66727783) 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, 33363890 + 33363891.

It is an arithmetic number, because the mean of its divisors is an integer number (33363891).

Almost surely, 2^66727781 is an apocalyptic number.

It is an amenable number.

66727781 is a deficient number, since it is larger than the sum of its proper divisors (1).

66727781 is an equidigital number, since it uses as much as digits as its factorization.

66727781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 197568, while the sum is 44.

The square root of 66727781 is about 8168.7074252907. The cubic root of 66727781 is about 405.6039984362.

The spelling of 66727781 in words is "sixty-six million, seven hundred twenty-seven thousand, seven hundred eighty-one".