9975821 has 4 divisors (see below), whose sum is σ = 10562652. Its totient is φ = 9388992.

The previous prime is 9975803. The next prime is 9975827. The reversal of 9975821 is 1285799.

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 6786025 + 3189796 = 2605^2 + 1786^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9975821 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 (9975827) 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, 293390 + ... + 293423.

It is an arithmetic number, because the mean of its divisors is an integer number (2640663).

Almost surely, 2^9975821 is an apocalyptic number.

It is an amenable number.

9975821 is a deficient number, since it is larger than the sum of its proper divisors (586831).

9975821 is a wasteful number, since it uses less digits than its factorization.

9975821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 586830.

The product of its digits is 45360, while the sum is 41.

The square root of 9975821 is about 3158.4523108637. The cubic root of 9975821 is about 215.2696886121.

The spelling of 9975821 in words is "nine million, nine hundred seventy-five thousand, eight hundred twenty-one".