215606221 has 4 divisors (see below), whose sum is σ = 215925372. Its totient is φ = 215287072.

The previous prime is 215606203. The next prime is 215606233. The reversal of 215606221 is 122606512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 179184996 + 36421225 = 13386^2 + 6035^2 .

It is a cyclic number.

It is not a de Polignac number, because 215606221 - 2⁷ = 215606093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215606621) 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 in 3 ways as a sum of consecutive naturals, for example, 158560 + ... + 159913.

It is an arithmetic number, because the mean of its divisors is an integer number (53981343).

Almost surely, 2^215606221 is an apocalyptic number.

It is an amenable number.

215606221 is a deficient number, since it is larger than the sum of its proper divisors (319151).

215606221 is an equidigital number, since it uses as much as digits as its factorization.

215606221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319150.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 215606221 is about 14683.5357118100. The cubic root of 215606221 is about 599.6351680225.

The spelling of 215606221 in words is "two hundred fifteen million, six hundred six thousand, two hundred twenty-one".