21104521 has 6 divisors (see below), whose sum is σ = 21808266. Its totient is φ = 20422800.

The previous prime is 21104507. The next prime is 21104527. The reversal of 21104521 is 12540112.

It can be written as a sum of positive squares in only one way, i.e., 19927296 + 1177225 = 4464^2 + 1085^2 .

It is not a de Polignac number, because 21104521 - 2¹³ = 21096329 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21104495 and 21104504.

It is not an unprimeable number, because it can be changed into a prime (21104527) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 10020 + ... + 11941.

It is an arithmetic number, because the mean of its divisors is an integer number (3634711).

Almost surely, 2^21104521 is an apocalyptic number.

It is an amenable number.

21104521 is a deficient number, since it is larger than the sum of its proper divisors (703745).

21104521 is an equidigital number, since it uses as much as digits as its factorization.

21104521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22023 (or 21992 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21104521 is about 4593.9657160236. The cubic root of 21104521 is about 276.3493833772.

Adding to 21104521 its reverse (12540112), we get a palindrome (33644633).

The spelling of 21104521 in words is "twenty-one million, one hundred four thousand, five hundred twenty-one".