20551221 has 12 divisors (see below), whose sum is σ = 29728972. Its totient is φ = 13680576.

The previous prime is 20551207. The next prime is 20551229. The reversal of 20551221 is 12215502.

It can be written as a sum of positive squares in 2 ways, for example, as 10150596 + 10400625 = 3186^2 + 3225^2 .

It is not a de Polignac number, because 20551221 - 2¹¹ = 20549173 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20551194 and 20551203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20551229) 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 11 ways as a sum of consecutive naturals, for example, 7215 + ... + 9651.

Almost surely, 2^20551221 is an apocalyptic number.

It is an amenable number.

20551221 is a deficient number, since it is larger than the sum of its proper divisors (9177751).

20551221 is a wasteful number, since it uses less digits than its factorization.

20551221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3380 (or 3377 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 20551221 is about 4533.3454534152. The cubic root of 20551221 is about 273.9129360905.

Adding to 20551221 its reverse (12215502), we get a palindrome (32766723).

The spelling of 20551221 in words is "twenty million, five hundred fifty-one thousand, two hundred twenty-one".