21112521 has 16 divisors (see below), whose sum is σ = 29916864. Its totient is φ = 13197824.

The previous prime is 21112433. The next prime is 21112547. The reversal of 21112521 is 12521112.

It is a cyclic number.

It is not a de Polignac number, because 21112521 - 2⁹ = 21112009 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21112521.

It is not an unprimeable number, because it can be changed into a prime (21112561) 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, 17101 + ... + 18293.

It is an arithmetic number, because the mean of its divisors is an integer number (1869804).

Almost surely, 2^21112521 is an apocalyptic number.

It is an amenable number.

21112521 is a deficient number, since it is larger than the sum of its proper divisors (8804343).

21112521 is a wasteful number, since it uses less digits than its factorization.

21112521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1560.

The product of its digits is 40, while the sum is 15.

The square root of 21112521 is about 4594.8363409375. The cubic root of 21112521 is about 276.3842971568.

Adding to 21112521 its reverse (12521112), we get a palindrome (33633633).

The spelling of 21112521 in words is "twenty-one million, one hundred twelve thousand, five hundred twenty-one".