21036521 has 16 divisors (see below), whose sum is σ = 23623488. Its totient is φ = 18571200.

The previous prime is 21036517. The next prime is 21036527. The reversal of 21036521 is 12563012.

It is a cyclic number.

It is not a de Polignac number, because 21036521 - 2² = 21036517 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21036493 and 21036502.

It is not an unprimeable number, because it can be changed into a prime (21036527) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 71651 + ... + 71943.

It is an arithmetic number, because the mean of its divisors is an integer number (1476468).

Almost surely, 2^21036521 is an apocalyptic number.

It is an amenable number.

21036521 is a deficient number, since it is larger than the sum of its proper divisors (2586967).

21036521 is a wasteful number, since it uses less digits than its factorization.

21036521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 472.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21036521 is about 4586.5587317727. The cubic root of 21036521 is about 276.0522594104.

Adding to 21036521 its reverse (12563012), we get a palindrome (33599533).

The spelling of 21036521 in words is "twenty-one million, thirty-six thousand, five hundred twenty-one".