28138609 has 4 divisors (see below), whose sum is σ = 28168560. Its totient is φ = 28108660.

The previous prime is 28138603. The next prime is 28138631. The reversal of 28138609 is 90683182.

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, and also an emirpimes, since its reverse is a distinct semiprime: 90683182 = 2 ⋅45341591.

It is a cyclic number.

It is not a de Polignac number, because 28138609 - 2²³ = 19750001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28138603) 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, 13519 + ... + 15460.

It is an arithmetic number, because the mean of its divisors is an integer number (7042140).

Almost surely, 2^28138609 is an apocalyptic number.

It is an amenable number.

28138609 is a deficient number, since it is larger than the sum of its proper divisors (29951).

28138609 is an equidigital number, since it uses as much as digits as its factorization.

28138609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29950.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 28138609 is about 5304.5837725499. The cubic root of 28138609 is about 304.1591423505.

The spelling of 28138609 in words is "twenty-eight million, one hundred thirty-eight thousand, six hundred nine".