9918221 has 6 divisors (see below), whose sum is σ = 10368750. Its totient is φ = 9486488.

The previous prime is 9918217. The next prime is 9918253. The reversal of 9918221 is 1228199.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 8940100 + 978121 = 2990^2 + 989^2 .

It is not a de Polignac number, because 9918221 - 2² = 9918217 is a prime.

It is a super-2 number, since 2×9918221² = 196742215609682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9918121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8846 + ... + 9903.

It is an arithmetic number, because the mean of its divisors is an integer number (1728125).

Almost surely, 2^9918221 is an apocalyptic number.

It is an amenable number.

9918221 is a deficient number, since it is larger than the sum of its proper divisors (450529).

9918221 is a wasteful number, since it uses less digits than its factorization.

9918221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18795 (or 18772 counting only the distinct ones).

The product of its digits is 2592, while the sum is 32.

The square root of 9918221 is about 3149.3207204094. The cubic root of 9918221 is about 214.8545690371.

The spelling of 9918221 in words is "nine million, nine hundred eighteen thousand, two hundred twenty-one".