28043721 has 12 divisors (see below), whose sum is σ = 41113072. Its totient is φ = 18416376.

The previous prime is 28043711. The next prime is 28043777. The reversal of 28043721 is 12734082.

It is not a de Polignac number, because 28043721 - 2¹⁰ = 28042697 is a prime.

It is a super-3 number, since 3×28043721³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (28043711) 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, 22651 + ... + 23856.

Almost surely, 2^28043721 is an apocalyptic number.

It is an amenable number.

28043721 is a deficient number, since it is larger than the sum of its proper divisors (13069351).

28043721 is a wasteful number, since it uses less digits than its factorization.

28043721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46580 (or 46577 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 28043721 is about 5295.6322568698. The cubic root of 28043721 is about 303.8168658363.

The spelling of 28043721 in words is "twenty-eight million, forty-three thousand, seven hundred twenty-one".