21222515 has 4 divisors (see below), whose sum is σ = 25467024. Its totient is φ = 16978008.

The previous prime is 21222503. The next prime is 21222529. The reversal of 21222515 is 51522212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21222515 - 2⁴ = 21222499 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2122247 + ... + 2122256.

It is an arithmetic number, because the mean of its divisors is an integer number (6366756).

Almost surely, 2^21222515 is an apocalyptic number.

21222515 is a deficient number, since it is larger than the sum of its proper divisors (4244509).

21222515 is an equidigital number, since it uses as much as digits as its factorization.

21222515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4244508.

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

The square root of 21222515 is about 4606.7900972369. The cubic root of 21222515 is about 276.8634436626.

Adding to 21222515 its reverse (51522212), we get a palindrome (72744727).

The spelling of 21222515 in words is "twenty-one million, two hundred twenty-two thousand, five hundred fifteen".