15552721 has 4 divisors (see below), whose sum is σ = 15576372. Its totient is φ = 15529072.

The previous prime is 15552709. The next prime is 15552727. The reversal of 15552721 is 12725551.

15552721 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.

It can be written as a sum of positive squares in 2 ways, for example, as 13242321 + 2310400 = 3639^2 + 1520^2 .

It is a cyclic number.

It is not a de Polignac number, because 15552721 - 2¹¹ = 15550673 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 15552721.

It is not an unprimeable number, because it can be changed into a prime (15552727) 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, 10810 + ... + 12163.

It is an arithmetic number, because the mean of its divisors is an integer number (3894093).

Almost surely, 2^15552721 is an apocalyptic number.

It is an amenable number.

15552721 is a deficient number, since it is larger than the sum of its proper divisors (23651).

15552721 is an equidigital number, since it uses as much as digits as its factorization.

15552721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23650.

The product of its digits is 3500, while the sum is 28.

The square root of 15552721 is about 3943.6938268583. The cubic root of 15552721 is about 249.6139160637.

The spelling of 15552721 in words is "fifteen million, five hundred fifty-two thousand, seven hundred twenty-one".