21225521 has 8 divisors (see below), whose sum is σ = 21772800. Its totient is φ = 20685280.

The previous prime is 21225511. The next prime is 21225541. The reversal of 21225521 is 12552212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21225521 - 2¹⁸ = 20963377 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21225493 and 21225502.

It is not an unprimeable number, because it can be changed into a prime (21225511) 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, 4640 + ... + 7998.

It is an arithmetic number, because the mean of its divisors is an integer number (2721600).

Almost surely, 2^21225521 is an apocalyptic number.

It is an amenable number.

21225521 is a deficient number, since it is larger than the sum of its proper divisors (547279).

21225521 is an equidigital number, since it uses as much as digits as its factorization.

21225521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3519.

The product of its digits is 400, while the sum is 20.

The square root of 21225521 is about 4607.1163432238. The cubic root of 21225521 is about 276.8765148784.

Adding to 21225521 its reverse (12552212), we get a palindrome (33777733).

The spelling of 21225521 in words is "twenty-one million, two hundred twenty-five thousand, five hundred twenty-one".