9966661 has 4 divisors (see below), whose sum is σ = 9973024. Its totient is φ = 9960300.

The previous prime is 9966643. The next prime is 9966667. The reversal of 9966661 is 1666699.

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, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1666699 = 19 ⋅87721.

It is a cyclic number.

It is not a de Polignac number, because 9966661 - 2⁵ = 9966629 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9966667) 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, 1006 + ... + 4576.

It is an arithmetic number, because the mean of its divisors is an integer number (2493256).

Almost surely, 2^9966661 is an apocalyptic number.

It is an amenable number.

9966661 is a deficient number, since it is larger than the sum of its proper divisors (6363).

9966661 is a wasteful number, since it uses less digits than its factorization.

9966661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6362.

The product of its digits is 104976, while the sum is 43.

The square root of 9966661 is about 3157.0019005379. The cubic root of 9966661 is about 215.2037801121.

The spelling of 9966661 in words is "nine million, nine hundred sixty-six thousand, six hundred sixty-one".