28728109 has 4 divisors (see below), whose sum is σ = 28996704. Its totient is φ = 28459516.

The previous prime is 28728097. The next prime is 28728121. The reversal of 28728109 is 90182782.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (28728097) and next prime (28728121).

It is a cyclic number.

It is not a de Polignac number, because 28728109 - 2²¹ = 26630957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28728709) 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, 134137 + ... + 134350.

It is an arithmetic number, because the mean of its divisors is an integer number (7249176).

Almost surely, 2^28728109 is an apocalyptic number.

It is an amenable number.

28728109 is a deficient number, since it is larger than the sum of its proper divisors (268595).

28728109 is a wasteful number, since it uses less digits than its factorization.

28728109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 268594.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 28728109 is about 5359.8609123745. The cubic root of 28728109 is about 306.2685106679.

The spelling of 28728109 in words is "twenty-eight million, seven hundred twenty-eight thousand, one hundred nine".