15672721 has 4 divisors (see below), whose sum is σ = 15685092. Its totient is φ = 15660352.

The previous prime is 15672697. The next prime is 15672733. The reversal of 15672721 is 12727651.

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 14137600 + 1535121 = 3760^2 + 1239^2 .

It is a cyclic number.

It is not a de Polignac number, because 15672721 - 2⁷ = 15672593 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15672221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4036 + ... + 6901.

It is an arithmetic number, because the mean of its divisors is an integer number (3921273).

Almost surely, 2^15672721 is an apocalyptic number.

It is an amenable number.

15672721 is a deficient number, since it is larger than the sum of its proper divisors (12371).

15672721 is a wasteful number, since it uses less digits than its factorization.

15672721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12370.

The product of its digits is 5880, while the sum is 31.

The square root of 15672721 is about 3958.8787554054. The cubic root of 15672721 is about 250.2542533333.

The spelling of 15672721 in words is "fifteen million, six hundred seventy-two thousand, seven hundred twenty-one".