It is a happy number.
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 a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12122251 = 2857 ⋅4243.
It is a cyclic number.
It is a Duffinian number.
Almost surely, 215222121 is an apocalyptic number.
It is an amenable number.
15222121 is an equidigital number, since it uses as much as digits as its factorization.
15222121 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 7910.
The square root of 15222121 is about 3901.5536648879. The cubic root of 15222121 is about 247.8325753860.
Adding to 15222121 its reverse (12122251), we get a palindrome (27344372).
The spelling of 15222121 in words is "fifteen million, two hundred twenty-two thousand, one hundred twenty-one".