66810861 has 24 divisors (see below), whose sum is σ = 104229216. Its totient is φ = 40995360.

The previous prime is 66810857. The next prime is 66810889. The reversal of 66810861 is 16801866.

It is not a de Polignac number, because 66810861 - 2² = 66810857 is a prime.

It is a super-2 number, since 2×66810861² = 8927382295122642, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66810811) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 56866 + ... + 58028.

It is an arithmetic number, because the mean of its divisors is an integer number (4342884).

Almost surely, 2^66810861 is an apocalyptic number.

It is an amenable number.

66810861 is a deficient number, since it is larger than the sum of its proper divisors (37418355).

66810861 is a wasteful number, since it uses less digits than its factorization.

66810861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1673 (or 1670 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 36.

The square root of 66810861 is about 8173.7911032764. The cubic root of 66810861 is about 405.7722622098.

The spelling of 66810861 in words is "sixty-six million, eight hundred ten thousand, eight hundred sixty-one".