28738721 has 16 divisors (see below), whose sum is σ = 33369408. Its totient is φ = 24460800.

The previous prime is 28738711. The next prime is 28738769. The reversal of 28738721 is 12783782.

It is a cyclic number.

It is not a de Polignac number, because 28738721 - 2⁶ = 28738657 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (28738711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 58286 + ... + 58776.

It is an arithmetic number, because the mean of its divisors is an integer number (2085588).

Almost surely, 2^28738721 is an apocalyptic number.

It is an amenable number.

28738721 is a deficient number, since it is larger than the sum of its proper divisors (4630687).

28738721 is a wasteful number, since it uses less digits than its factorization.

28738721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 832.

The product of its digits is 37632, while the sum is 38.

The square root of 28738721 is about 5360.8507720324. The cubic root of 28738721 is about 306.3062173071.

The spelling of 28738721 in words is "twenty-eight million, seven hundred thirty-eight thousand, seven hundred twenty-one".