21102521 has 24 divisors (see below), whose sum is σ = 24961440. Its totient is φ = 17772480.

The previous prime is 21102493. The next prime is 21102541. The reversal of 21102521 is 12520112.

It is not a de Polignac number, because 21102521 - 2¹⁸ = 20840377 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21102496 and 21102505.

It is not an unprimeable number, because it can be changed into a prime (21102541) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 153965 + ... + 154101.

It is an arithmetic number, because the mean of its divisors is an integer number (1040060).

Almost surely, 2^21102521 is an apocalyptic number.

It is an amenable number.

21102521 is a deficient number, since it is larger than the sum of its proper divisors (3858919).

21102521 is a wasteful number, since it uses less digits than its factorization.

21102521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 245 (or 234 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21102521 is about 4593.7480340132. The cubic root of 21102521 is about 276.3406535538.

Adding to 21102521 its reverse (12520112), we get a palindrome (33622633).

The spelling of 21102521 in words is "twenty-one million, one hundred two thousand, five hundred twenty-one".