21304521 has 12 divisors (see below), whose sum is σ = 35169472. Its totient is φ = 12173976.

The previous prime is 21304511. The next prime is 21304537. The reversal of 21304521 is 12540312.

21304521 is a `hidden beast` number, since 213 + 0 + 452 + 1 = 666.

It is not a de Polignac number, because 21304521 - 2⁶ = 21304457 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21304494 and 21304503.

It is not an unprimeable number, because it can be changed into a prime (21304501) 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, 169021 + ... + 169146.

Almost surely, 2^21304521 is an apocalyptic number.

21304521 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21304521 is a deficient number, since it is larger than the sum of its proper divisors (13864951).

21304521 is a wasteful number, since it uses less digits than its factorization.

21304521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 338180 (or 338177 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21304521 is about 4615.6820731069. The cubic root of 21304521 is about 277.2195950117.

Adding to 21304521 its reverse (12540312), we get a palindrome (33844833).

The spelling of 21304521 in words is "twenty-one million, three hundred four thousand, five hundred twenty-one".