20671221 has 12 divisors (see below), whose sum is σ = 29090112. Its totient is φ = 13054824.

The previous prime is 20671213. The next prime is 20671241. The reversal of 20671221 is 12217602.

It is not a de Polignac number, because 20671221 - 2³ = 20671213 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20671241) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8461 + ... + 10626.

It is an arithmetic number, because the mean of its divisors is an integer number (2424176).

Almost surely, 2^20671221 is an apocalyptic number.

It is an amenable number.

20671221 is a deficient number, since it is larger than the sum of its proper divisors (8418891).

20671221 is a wasteful number, since it uses less digits than its factorization.

20671221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19128 (or 19109 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 20671221 is about 4546.5614479516. The cubic root of 20671221 is about 274.4450339676.

Adding to 20671221 its reverse (12217602), we get a palindrome (32888823).

The spelling of 20671221 in words is "twenty million, six hundred seventy-one thousand, two hundred twenty-one".