7128409 has 4 divisors (see below), whose sum is σ = 7156404. Its totient is φ = 7100416.

The previous prime is 7128391. The next prime is 7128427. The reversal of 7128409 is 9048217.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (7128391) and next prime (7128427).

It can be written as a sum of positive squares in 2 ways, for example, as 6734025 + 394384 = 2595^2 + 628^2 .

It is a cyclic number.

It is not a de Polignac number, because 7128409 - 2⁷ = 7128281 is a prime.

It is a Duffinian number.

7128409 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (7128509) 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, 13612 + ... + 14125.

It is an arithmetic number, because the mean of its divisors is an integer number (1789101).

Almost surely, 2^7128409 is an apocalyptic number.

It is an amenable number.

7128409 is a deficient number, since it is larger than the sum of its proper divisors (27995).

7128409 is a wasteful number, since it uses less digits than its factorization.

7128409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27994.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 7128409 is about 2669.9080508512. The cubic root of 7128409 is about 192.4557406540.

The spelling of 7128409 in words is "seven million, one hundred twenty-eight thousand, four hundred nine".