918438221 has 2 divisors, whose sum is σ = 918438222. Its totient is φ = 918438220.

The previous prime is 918438217. The next prime is 918438223. The reversal of 918438221 is 122834819.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 900840196 + 17598025 = 30014^2 + 4195^2 .

It is a cyclic number.

It is not a de Polignac number, because 918438221 - 2² = 918438217 is a prime.

Together with 918438223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (918438223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 459219110 + 459219111.

It is an arithmetic number, because the mean of its divisors is an integer number (459219111).

Almost surely, 2^918438221 is an apocalyptic number.

It is an amenable number.

918438221 is a deficient number, since it is larger than the sum of its proper divisors (1).

918438221 is an equidigital number, since it uses as much as digits as its factorization.

918438221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27648, while the sum is 38.

The square root of 918438221 is about 30305.7456763565. The cubic root of 918438221 is about 972.0381634860.

The spelling of 918438221 in words is "nine hundred eighteen million, four hundred thirty-eight thousand, two hundred twenty-one".