15222221 has 4 divisors (see below), whose sum is σ = 17396832. Its totient is φ = 13047612.

The previous prime is 15222197. The next prime is 15222223. The reversal of 15222221 is 12222251.

15222221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12222251 = 557 ⋅21943.

It is a cyclic number.

It is not a de Polignac number, because 15222221 - 2¹⁰ = 15221197 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 15222221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15222223) 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, 1087295 + ... + 1087308.

It is an arithmetic number, because the mean of its divisors is an integer number (4349208).

Almost surely, 2^15222221 is an apocalyptic number.

It is an amenable number.

15222221 is a deficient number, since it is larger than the sum of its proper divisors (2174611).

15222221 is an equidigital number, since it uses as much as digits as its factorization.

15222221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2174610.

The product of its digits is 160, while the sum is 17.

The square root of 15222221 is about 3901.5664802743. The cubic root of 15222221 is about 247.8331180875.

Adding to 15222221 its reverse (12222251), we get a palindrome (27444472).

The spelling of 15222221 in words is "fifteen million, two hundred twenty-two thousand, two hundred twenty-one".