28661309 has 4 divisors (see below), whose sum is σ = 29649660. Its totient is φ = 27672960.

The previous prime is 28661257. The next prime is 28661317. The reversal of 28661309 is 90316682.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16080100 + 12581209 = 4010^2 + 3547^2 .

It is not a de Polignac number, because 28661309 - 2⁸ = 28661053 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 (28661389) 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, 494132 + ... + 494189.

It is an arithmetic number, because the mean of its divisors is an integer number (7412415).

Almost surely, 2^28661309 is an apocalyptic number.

28661309 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

28661309 is a deficient number, since it is larger than the sum of its proper divisors (988351).

28661309 is an equidigital number, since it uses as much as digits as its factorization.

28661309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 988350.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 28661309 is about 5353.6257807209. The cubic root of 28661309 is about 306.0309429458.

The spelling of 28661309 in words is "twenty-eight million, six hundred sixty-one thousand, three hundred nine".