66006661 has 4 divisors (see below), whose sum is σ = 75436192. Its totient is φ = 56577132.

The previous prime is 66006649. The next prime is 66006667. The reversal of 66006661 is 16660066.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66006661 - 2¹³ = 65998469 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 (66006667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4714755 + ... + 4714768.

It is an arithmetic number, because the mean of its divisors is an integer number (18859048).

Almost surely, 2^66006661 is an apocalyptic number.

It is an amenable number.

66006661 is a deficient number, since it is larger than the sum of its proper divisors (9429531).

66006661 is an equidigital number, since it uses as much as digits as its factorization.

66006661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9429530.

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 66006661 is about 8124.4483505036. The cubic root of 66006661 is about 404.1375969078.

The spelling of 66006661 in words is "sixty-six million, six thousand, six hundred sixty-one".