66605661 has 12 divisors (see below), whose sum is σ = 98808892. Its totient is φ = 43203456.

The previous prime is 66605657. The next prime is 66605713. The reversal of 66605661 is 16650666.

It can be written as a sum of positive squares in 2 ways, for example, as 32558436 + 34047225 = 5706^2 + 5835^2 .

It is not a de Polignac number, because 66605661 - 2² = 66605657 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66605641) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 99676 + ... + 100341.

Almost surely, 2^66605661 is an apocalyptic number.

It is an amenable number.

66605661 is a deficient number, since it is larger than the sum of its proper divisors (32203231).

66605661 is a wasteful number, since it uses less digits than its factorization.

66605661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200060 (or 200057 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 36.

The square root of 66605661 is about 8161.2291353693. The cubic root of 66605661 is about 405.3564123631.

It can be divided in two parts, 6660 and 5661, that added together give a palindrome (12321).

The spelling of 66605661 in words is "sixty-six million, six hundred five thousand, six hundred sixty-one".