7128809 has 4 divisors (see below), whose sum is σ = 7374660. Its totient is φ = 6882960.

The previous prime is 7128799. The next prime is 7128817. The reversal of 7128809 is 9088217.

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: 9088217 = 17 ⋅534601.

It can be written as a sum of positive squares in 2 ways, for example, as 2111209 + 5017600 = 1453^2 + 2240^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7128809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7128509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 122882 + ... + 122939.

It is an arithmetic number, because the mean of its divisors is an integer number (1843665).

Almost surely, 2^7128809 is an apocalyptic number.

It is an amenable number.

7128809 is a deficient number, since it is larger than the sum of its proper divisors (245851).

7128809 is a wasteful number, since it uses less digits than its factorization.

7128809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245850.

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 7128809 is about 2669.9829587471. The cubic root of 7128809 is about 192.4593403753.

The spelling of 7128809 in words is "seven million, one hundred twenty-eight thousand, eight hundred nine".