66161666561 has 8 divisors (see below), whose sum is σ = 67531344000. Its totient is φ = 64800265680.

The previous prime is 66161666537. The next prime is 66161666581. The reversal of 66161666561 is 16566616166.

It is a happy number.

66161666561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 66161666561 - 2¹⁸ = 66161404417 is a prime.

It is a super-2 number, since 2×66161666561² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66161666521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2052986 + ... + 2084963.

It is an arithmetic number, because the mean of its divisors is an integer number (8441418000).

Almost surely, 2^66161666561 is an apocalyptic number.

It is an amenable number.

66161666561 is a deficient number, since it is larger than the sum of its proper divisors (1369677439).

66161666561 is a wasteful number, since it uses less digits than its factorization.

66161666561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4138279.

The product of its digits is 1399680, while the sum is 50.

The spelling of 66161666561 in words is "sixty-six billion, one hundred sixty-one million, six hundred sixty-six thousand, five hundred sixty-one".