9918221081 has 2 divisors, whose sum is σ = 9918221082. Its totient is φ = 9918221080.

The previous prime is 9918220889. The next prime is 9918221099. The reversal of 9918221081 is 1801228199.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9567969856 + 350251225 = 97816^2 + 18715^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9918221081 is a prime.

It is a super-3 number, since 3×9918221081³ (a number of 31 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (9918221381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4959110540 + 4959110541.

It is an arithmetic number, because the mean of its divisors is an integer number (4959110541).

Almost surely, 2^9918221081 is an apocalyptic number.

It is an amenable number.

9918221081 is a deficient number, since it is larger than the sum of its proper divisors (1).

9918221081 is an equidigital number, since it uses as much as digits as its factorization.

9918221081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20736, while the sum is 41.

The square root of 9918221081 is about 99590.2659952267. The cubic root of 9918221081 is about 2148.5456962199.

The spelling of 9918221081 in words is "nine billion, nine hundred eighteen million, two hundred twenty-one thousand, eighty-one".