21221586 has 12 divisors (see below), whose sum is σ = 45980142. Its totient is φ = 7073856.

The previous prime is 21221579. The next prime is 21221597. The reversal of 21221586 is 68512212.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 19580625 + 1640961 = 4425^2 + 1281^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 589471 + ... + 589506.

Almost surely, 2^21221586 is an apocalyptic number.

21221586 is an abundant number, since it is smaller than the sum of its proper divisors (24758556).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21221586 is a wasteful number, since it uses less digits than its factorization.

21221586 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1178985 (or 1178982 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 21221586 is about 4606.6892667077. The cubic root of 21221586 is about 276.8594037724.

Adding to 21221586 its reverse (68512212), we get a palindrome (89733798).

The spelling of 21221586 in words is "twenty-one million, two hundred twenty-one thousand, five hundred eighty-six".