648128609 has 4 divisors (see below), whose sum is σ = 648478740. Its totient is φ = 647778480.

The previous prime is 648128603. The next prime is 648128623. The reversal of 648128609 is 906821846.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 320410000 + 327718609 = 17900^2 + 18103^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-648128609 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 648128609.

It is not an unprimeable number, because it can be changed into a prime (648128603) 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, 172274 + ... + 175995.

It is an arithmetic number, because the mean of its divisors is an integer number (162119685).

Almost surely, 2^648128609 is an apocalyptic number.

It is an amenable number.

648128609 is a deficient number, since it is larger than the sum of its proper divisors (350131).

648128609 is a wasteful number, since it uses less digits than its factorization.

648128609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350130.

The product of its (nonzero) digits is 165888, while the sum is 44.

The square root of 648128609 is about 25458.3701167219. The cubic root of 648128609 is about 865.4069872478.

The spelling of 648128609 in words is "six hundred forty-eight million, one hundred twenty-eight thousand, six hundred nine".