20665221 has 4 divisors (see below), whose sum is σ = 27553632. Its totient is φ = 13776812.

The previous prime is 20665213. The next prime is 20665237. The reversal of 20665221 is 12256602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20665221 - 2³ = 20665213 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20665191 and 20665200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20665261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3444201 + ... + 3444206.

It is an arithmetic number, because the mean of its divisors is an integer number (6888408).

Almost surely, 2^20665221 is an apocalyptic number.

It is an amenable number.

20665221 is a deficient number, since it is larger than the sum of its proper divisors (6888411).

20665221 is an equidigital number, since it uses as much as digits as its factorization.

20665221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6888410.

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 20665221 is about 4545.9015607468. The cubic root of 20665221 is about 274.4184780528.

The spelling of 20665221 in words is "twenty million, six hundred sixty-five thousand, two hundred twenty-one".