999221 has 2 divisors, whose sum is σ = 999222. Its totient is φ = 999220.

The previous prime is 999217. The next prime is 999233. The reversal of 999221 is 122999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 902500 + 96721 = 950^2 + 311^2 .

It is a cyclic number.

It is not a de Polignac number, because 999221 - 2² = 999217 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is equal to p₇₈₄₄₉ and since 999221 and 78449 have the same sum of digits, it is a Honaker prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499610 + 499611.

It is an arithmetic number, because the mean of its divisors is an integer number (499611).

2⁹⁹⁹²²¹ is an apocalyptic number.

It is an amenable number.

999221 is a deficient number, since it is larger than the sum of its proper divisors (1).

999221 is an equidigital number, since it uses as much as digits as its factorization.

999221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2916, while the sum is 32.

The square root of 999221 is about 999.6104241153. The cubic root of 999221 is about 99.9740265877.

The spelling of 999221 in words is "nine hundred ninety-nine thousand, two hundred twenty-one".