21522209 has 4 divisors (see below), whose sum is σ = 21843504. Its totient is φ = 21200916.

The previous prime is 21522173. The next prime is 21522217. The reversal of 21522209 is 90222512.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21522209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21522509) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 160547 + ... + 160680.

It is an arithmetic number, because the mean of its divisors is an integer number (5460876).

Almost surely, 2^21522209 is an apocalyptic number.

It is an amenable number.

21522209 is a deficient number, since it is larger than the sum of its proper divisors (321295).

21522209 is an equidigital number, since it uses as much as digits as its factorization.

21522209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321294.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21522209 is about 4639.2034876690. The cubic root of 21522209 is about 278.1606002319.

The spelling of 21522209 in words is "twenty-one million, five hundred twenty-two thousand, two hundred nine".