28728613 has 4 divisors (see below), whose sum is σ = 29505100. Its totient is φ = 27952128.

The previous prime is 28728607. The next prime is 28728631. The reversal of 28728613 is 31682782.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31682782 = 2 ⋅15841391.

It can be written as a sum of positive squares in 2 ways, for example, as 25220484 + 3508129 = 5022^2 + 1873^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28728613 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 776449 = 28728613 / (2 + 8 + 7 + 2 + 8 + 6 + 1 + 3).

It is a Duffinian number.

It is a nialpdrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28728673) 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, 388188 + ... + 388261.

It is an arithmetic number, because the mean of its divisors is an integer number (7376275).

Almost surely, 2^28728613 is an apocalyptic number.

It is an amenable number.

28728613 is a deficient number, since it is larger than the sum of its proper divisors (776487).

28728613 is an equidigital number, since it uses as much as digits as its factorization.

28728613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 776486.

The product of its digits is 32256, while the sum is 37.

The square root of 28728613 is about 5359.9079283137. The cubic root of 28728613 is about 306.2703016945.

It can be divided in two parts, 287 and 28613, that added together give a square (28900 = 170²).

The spelling of 28728613 in words is "twenty-eight million, seven hundred twenty-eight thousand, six hundred thirteen".