28160721 has 12 divisors (see below), whose sum is σ = 43069572. Its totient is φ = 17669376.

The previous prime is 28160707. The next prime is 28160729. The reversal of 28160721 is 12706182.

It can be written as a sum of positive squares in 2 ways, for example, as 26378496 + 1782225 = 5136^2 + 1335^2 .

It is not a de Polignac number, because 28160721 - 2¹¹ = 28158673 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28160729) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 91876 + ... + 92181.

It is an arithmetic number, because the mean of its divisors is an integer number (3589131).

Almost surely, 2^28160721 is an apocalyptic number.

It is an amenable number.

28160721 is a deficient number, since it is larger than the sum of its proper divisors (14908851).

28160721 is a wasteful number, since it uses less digits than its factorization.

28160721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184080 (or 184077 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 28160721 is about 5306.6675984086. The cubic root of 28160721 is about 304.2387933622.

The spelling of 28160721 in words is "twenty-eight million, one hundred sixty thousand, seven hundred twenty-one".