21621136 has 20 divisors (see below), whose sum is σ = 43243264. Its totient is φ = 10461600.

The previous prime is 21621121. The next prime is 21621137. The reversal of 21621136 is 63112612.

21621136 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21621137) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 21300 + ... + 22291.

Almost surely, 2^21621136 is an apocalyptic number.

It is an amenable number.

21621136 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21621136 is a wasteful number, since it uses less digits than its factorization.

21621136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43630 (or 43624 counting only the distinct ones).

The product of its digits is 432, while the sum is 22.

The square root of 21621136 is about 4649.8533310202. The cubic root of 21621136 is about 278.5861380167.

Adding to 21621136 its reverse (63112612), we get a palindrome (84733748).

The spelling of 21621136 in words is "twenty-one million, six hundred twenty-one thousand, one hundred thirty-six".