28505561 has 4 divisors (see below), whose sum is σ = 32577792. Its totient is φ = 24433332.

The previous prime is 28505557. The next prime is 28505563. The reversal of 28505561 is 16550582.

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: 16550582 = 2 ⋅8275291.

It is not a de Polignac number, because 28505561 - 2² = 28505557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28505563) 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, 2036105 + ... + 2036118.

It is an arithmetic number, because the mean of its divisors is an integer number (8144448).

Almost surely, 2^28505561 is an apocalyptic number.

It is an amenable number.

28505561 is a deficient number, since it is larger than the sum of its proper divisors (4072231).

28505561 is an equidigital number, since it uses as much as digits as its factorization.

28505561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4072230.

The product of its (nonzero) digits is 12000, while the sum is 32.

The square root of 28505561 is about 5339.0599359812. The cubic root of 28505561 is about 305.4756030494.

The spelling of 28505561 in words is "twenty-eight million, five hundred five thousand, five hundred sixty-one".