21122521 has 8 divisors (see below), whose sum is σ = 24221120. Its totient is φ = 18044208.

The previous prime is 21122473. The next prime is 21122561. The reversal of 21122521 is 12522112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21122521 - 2⁷ = 21122393 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21122495 and 21122504.

It is not an unprimeable number, because it can be changed into a prime (21122561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2766 + ... + 7063.

It is an arithmetic number, because the mean of its divisors is an integer number (3027640).

Almost surely, 2^21122521 is an apocalyptic number.

It is an amenable number.

21122521 is a deficient number, since it is larger than the sum of its proper divisors (3098599).

21122521 is an equidigital number, since it uses as much as digits as its factorization.

21122521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10143.

The product of its digits is 80, while the sum is 16.

The square root of 21122521 is about 4595.9243901526. The cubic root of 21122521 is about 276.4279269807.

Adding to 21122521 its reverse (12522112), we get a palindrome (33644633).

The spelling of 21122521 in words is "twenty-one million, one hundred twenty-two thousand, five hundred twenty-one".