66809561 has 8 divisors (see below), whose sum is σ = 82227264. Its totient is φ = 52860240.

The previous prime is 66809551. The next prime is 66809569. The reversal of 66809561 is 16590866.

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 66809561 - 2¹⁸ = 66547417 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66809569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 366995 + ... + 367176.

It is an arithmetic number, because the mean of its divisors is an integer number (10278408).

Almost surely, 2^66809561 is an apocalyptic number.

It is an amenable number.

66809561 is a deficient number, since it is larger than the sum of its proper divisors (15417703).

66809561 is a wasteful number, since it uses less digits than its factorization.

66809561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 734191.

The product of its (nonzero) digits is 77760, while the sum is 41.

The square root of 66809561 is about 8173.7115804266. The cubic root of 66809561 is about 405.7696303655.

The spelling of 66809561 in words is "sixty-six million, eight hundred nine thousand, five hundred sixty-one".