28991005 has 4 divisors (see below), whose sum is σ = 34789212. Its totient is φ = 23192800.

The previous prime is 28990991. The next prime is 28991009. The reversal of 28991005 is 50019982.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50019982 = 2 ⋅25009991.

It can be written as a sum of positive squares in 2 ways, for example, as 9108324 + 19882681 = 3018^2 + 4459^2 .

It is not a de Polignac number, because 28991005 - 2⁷ = 28990877 is a prime.

It is a super-3 number, since 3×28991005³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28991009) 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, 2899096 + ... + 2899105.

It is an arithmetic number, because the mean of its divisors is an integer number (8697303).

Almost surely, 2^28991005 is an apocalyptic number.

It is an amenable number.

28991005 is a deficient number, since it is larger than the sum of its proper divisors (5798207).

28991005 is an equidigital number, since it uses as much as digits as its factorization.

28991005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5798206.

The product of its (nonzero) digits is 6480, while the sum is 34.

The square root of 28991005 is about 5384.3295775797. The cubic root of 28991005 is about 307.1999143530.

The spelling of 28991005 in words is "twenty-eight million, nine hundred ninety-one thousand, five".