15172221 has 4 divisors (see below), whose sum is σ = 20229632. Its totient is φ = 10114812.

The previous prime is 15172193. The next prime is 15172231. The reversal of 15172221 is 12227151.

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: 12227151 = 3 ⋅4075717.

It is not a de Polignac number, because 15172221 - 2⁷ = 15172093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15172231) 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, 2528701 + ... + 2528706.

It is an arithmetic number, because the mean of its divisors is an integer number (5057408).

Almost surely, 2^15172221 is an apocalyptic number.

It is an amenable number.

15172221 is a deficient number, since it is larger than the sum of its proper divisors (5057411).

15172221 is an equidigital number, since it uses as much as digits as its factorization.

15172221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5057410.

The product of its digits is 280, while the sum is 21.

The square root of 15172221 is about 3895.1535271411. The cubic root of 15172221 is about 247.5614702944.

Adding to 15172221 its reverse (12227151), we get a palindrome (27399372).

The spelling of 15172221 in words is "fifteen million, one hundred seventy-two thousand, two hundred twenty-one".