66661881 has 24 divisors (see below), whose sum is σ = 105003936. Its totient is φ = 37290240.

The previous prime is 66661867. The next prime is 66661883. The reversal of 66661881 is 18816666.

It is not a de Polignac number, because 66661881 - 2⁵ = 66661849 is a prime.

It is a super-2 number, since 2×66661881² = 8887612756916322, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66661883) 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, 400 + ... + 11553.

It is an arithmetic number, because the mean of its divisors is an integer number (4375164).

Almost surely, 2^66661881 is an apocalyptic number.

It is an amenable number.

66661881 is a deficient number, since it is larger than the sum of its proper divisors (38342055).

66661881 is a wasteful number, since it uses less digits than its factorization.

66661881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11993 (or 11980 counting only the distinct ones).

The product of its digits is 82944, while the sum is 42.

The square root of 66661881 is about 8164.6727429824. The cubic root of 66661881 is about 405.4704303423.

The spelling of 66661881 in words is "sixty-six million, six hundred sixty-one thousand, eight hundred eighty-one".