20918221 has 8 divisors (see below), whose sum is σ = 22216320. Its totient is φ = 19639872.

The previous prime is 20918203. The next prime is 20918237. The reversal of 20918221 is 12281902.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20918221 - 2⁵ = 20918189 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20918291) 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 7 ways as a sum of consecutive naturals, for example, 2725 + ... + 7018.

It is an arithmetic number, because the mean of its divisors is an integer number (2777040).

Almost surely, 2^20918221 is an apocalyptic number.

It is an amenable number.

20918221 is a deficient number, since it is larger than the sum of its proper divisors (1298099).

20918221 is a wasteful number, since it uses less digits than its factorization.

20918221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9875.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 20918221 is about 4573.6441706805. The cubic root of 20918221 is about 275.5338214939.

The spelling of 20918221 in words is "twenty million, nine hundred eighteen thousand, two hundred twenty-one".