66156561 has 32 divisors (see below), whose sum is σ = 101243520. Its totient is φ = 42674112.

The previous prime is 66156557. The next prime is 66156577. The reversal of 66156561 is 16565166.

66156561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 66156561 - 2² = 66156557 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66156551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 118495 + ... + 119051.

It is an arithmetic number, because the mean of its divisors is an integer number (3163860).

Almost surely, 2^66156561 is an apocalyptic number.

It is an amenable number.

66156561 is a deficient number, since it is larger than the sum of its proper divisors (35086959).

66156561 is a wasteful number, since it uses less digits than its factorization.

66156561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 702 (or 696 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 66156561 is about 8133.6683605861. The cubic root of 66156561 is about 404.4432954729.

The spelling of 66156561 in words is "sixty-six million, one hundred fifty-six thousand, five hundred sixty-one".