9966821 has 4 divisors (see below), whose sum is σ = 10017612. Its totient is φ = 9916032.

The previous prime is 9966799. The next prime is 9966823. The reversal of 9966821 is 1286699.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7896100 + 2070721 = 2810^2 + 1439^2 .

It is a cyclic number.

It is not a de Polignac number, because 9966821 - 2¹⁰ = 9965797 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 (9966823) 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, 25100 + ... + 25493.

It is an arithmetic number, because the mean of its divisors is an integer number (2504403).

Almost surely, 2^9966821 is an apocalyptic number.

It is an amenable number.

9966821 is a deficient number, since it is larger than the sum of its proper divisors (50791).

9966821 is a wasteful number, since it uses less digits than its factorization.

9966821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50790.

The product of its digits is 46656, while the sum is 41.

The square root of 9966821 is about 3157.0272409341. The cubic root of 9966821 is about 215.2049316988.

The spelling of 9966821 in words is "nine million, nine hundred sixty-six thousand, eight hundred twenty-one".