28940809 has 4 divisors (see below), whose sum is σ = 29486916. Its totient is φ = 28394704.

The previous prime is 28940797. The next prime is 28940881. The reversal of 28940809 is 90804982.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90804982 = 2 ⋅45402491.

It can be written as a sum of positive squares in 2 ways, for example, as 7038409 + 21902400 = 2653^2 + 4680^2 .

It is a cyclic number.

It is not a de Polignac number, because 28940809 - 2²¹ = 26843657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28940209) 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, 272974 + ... + 273079.

It is an arithmetic number, because the mean of its divisors is an integer number (7371729).

Almost surely, 2^28940809 is an apocalyptic number.

It is an amenable number.

28940809 is a deficient number, since it is larger than the sum of its proper divisors (546107).

28940809 is an equidigital number, since it uses as much as digits as its factorization.

28940809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546106.

The product of its (nonzero) digits is 41472, while the sum is 40.

The square root of 28940809 is about 5379.6662535886. Note that the first 3 decimals coincide. The cubic root of 28940809 is about 307.0225131767.

The spelling of 28940809 in words is "twenty-eight million, nine hundred forty thousand, eight hundred nine".