66855881 has 2 divisors, whose sum is σ = 66855882. Its totient is φ = 66855880.

The previous prime is 66855827. The next prime is 66855907. The reversal of 66855881 is 18855866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 59043856 + 7812025 = 7684^2 + 2795^2 .

It is a cyclic number.

It is not a de Polignac number, because 66855881 - 2¹⁴ = 66839497 is a prime.

It is a super-2 number, since 2×66855881² = 8939417648572322, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (66851881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33427940 + 33427941.

It is an arithmetic number, because the mean of its divisors is an integer number (33427941).

Almost surely, 2^66855881 is an apocalyptic number.

It is an amenable number.

66855881 is a deficient number, since it is larger than the sum of its proper divisors (1).

66855881 is an equidigital number, since it uses as much as digits as its factorization.

66855881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 460800, while the sum is 47.

The square root of 66855881 is about 8176.5445635672. The cubic root of 66855881 is about 405.8633839490.

The spelling of 66855881 in words is "sixty-six million, eight hundred fifty-five thousand, eight hundred eighty-one".