818705221 has 2 divisors, whose sum is σ = 818705222. Its totient is φ = 818705220.

The previous prime is 818705219. The next prime is 818705233. The reversal of 818705221 is 122507818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 662805025 + 155900196 = 25745^2 + 12486^2 .

It is a cyclic number.

It is not a de Polignac number, because 818705221 - 2¹ = 818705219 is a prime.

Together with 818705219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (818705201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 409352610 + 409352611.

It is an arithmetic number, because the mean of its divisors is an integer number (409352611).

Almost surely, 2^818705221 is an apocalyptic number.

It is an amenable number.

818705221 is a deficient number, since it is larger than the sum of its proper divisors (1).

818705221 is an equidigital number, since it uses as much as digits as its factorization.

818705221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8960, while the sum is 34.

The square root of 818705221 is about 28613.0253730709. The cubic root of 818705221 is about 935.4972603509.

The spelling of 818705221 in words is "eight hundred eighteen million, seven hundred five thousand, two hundred twenty-one".