22521 has 4 divisors (see below), whose sum is σ = 30032. Its totient is φ = 15012.

The previous prime is 22511. The next prime is 22531. The reversal of 22521 is 12522.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (22511) and next prime (22531).

It is a de Polignac number, because none of the positive numbers 2^k-22521 is a prime.

It is a D-number.

It is a Duffinian number.

22521 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 22497 and 22506.

It is not an unprimeable number, because it can be changed into a prime (22501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3751 + ... + 3756.

It is an arithmetic number, because the mean of its divisors is an integer number (7508).

2²²⁵²¹ is an apocalyptic number.

It is an amenable number.

22521 is a deficient number, since it is larger than the sum of its proper divisors (7511).

22521 is an equidigital number, since it uses as much as digits as its factorization.

22521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7510.

The product of its digits is 40, while the sum is 12.

The square root of 22521 is about 150.0699836743. The cubic root of 22521 is about 28.2398611383.

Subtracting from 22521 its reverse (12522), we obtain a palindrome (9999).

The spelling of 22521 in words is "twenty-two thousand, five hundred twenty-one".