9990561 has 40 divisors (see below), whose sum is σ = 16581920. Its totient is φ = 5334336.

The previous prime is 9990557. The next prime is 9990569. The reversal of 9990561 is 1650999.

It is not a de Polignac number, because 9990561 - 2² = 9990557 is a prime.

It is a super-2 number, since 2×9990561² = 199622618189442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9990569) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 136821 + ... + 136893.

It is an arithmetic number, because the mean of its divisors is an integer number (414548).

Almost surely, 2^9990561 is an apocalyptic number.

It is an amenable number.

9990561 is a deficient number, since it is larger than the sum of its proper divisors (6591359).

9990561 is an equidigital number, since it uses as much as digits as its factorization.

9990561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123 (or 102 counting only the distinct ones).

The product of its (nonzero) digits is 21870, while the sum is 39.

The square root of 9990561 is about 3160.7848708825. The cubic root of 9990561 is about 215.3756619676.

The spelling of 9990561 in words is "nine million, nine hundred ninety thousand, five hundred sixty-one".