15724221 has 4 divisors (see below), whose sum is σ = 20965632. Its totient is φ = 10482812.

The previous prime is 15724217. The next prime is 15724237. The reversal of 15724221 is 12242751.

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 not a de Polignac number, because 15724221 - 2² = 15724217 is a prime.

It is a super-2 number, since 2×15724221² = 494502252113682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 15724191 and 15724200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15724211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2620701 + ... + 2620706.

It is an arithmetic number, because the mean of its divisors is an integer number (5241408).

Almost surely, 2^15724221 is an apocalyptic number.

It is an amenable number.

15724221 is a deficient number, since it is larger than the sum of its proper divisors (5241411).

15724221 is an equidigital number, since it uses as much as digits as its factorization.

15724221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5241410.

The product of its digits is 1120, while the sum is 24.

The square root of 15724221 is about 3965.3777878028. The cubic root of 15724221 is about 250.5280624814.

Adding to 15724221 its reverse (12242751), we get a palindrome (27966972).

The spelling of 15724221 in words is "fifteen million, seven hundred twenty-four thousand, two hundred twenty-one".