918191918221 has 2 divisors, whose sum is σ = 918191918222. Its totient is φ = 918191918220.

The previous prime is 918191918159. The next prime is 918191918279. The reversal of 918191918221 is 122819191819.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 813037642596 + 105154275625 = 901686^2 + 324275^2 .

It is a cyclic number.

It is not a de Polignac number, because 918191918221 - 2¹⁵ = 918191885453 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (918101918221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 459095959110 + 459095959111.

It is an arithmetic number, because the mean of its divisors is an integer number (459095959111).

Almost surely, 2^918191918221 is an apocalyptic number.

It is an amenable number.

918191918221 is a deficient number, since it is larger than the sum of its proper divisors (1).

918191918221 is an equidigital number, since it uses as much as digits as its factorization.

918191918221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 186624, while the sum is 52.

The spelling of 918191918221 in words is "nine hundred eighteen billion, one hundred ninety-one million, nine hundred eighteen thousand, two hundred twenty-one".