647665 has 4 divisors (see below), whose sum is σ = 777204. Its totient is φ = 518128.

The previous prime is 647663. The next prime is 647687. The reversal of 647665 is 566746.

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 461041 + 186624 = 679^2 + 432^2 .

It is a cyclic number.

It is not a de Polignac number, because 647665 - 2¹ = 647663 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 647665.

It is not an unprimeable number, because it can be changed into a prime (647663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64762 + ... + 64771.

It is an arithmetic number, because the mean of its divisors is an integer number (194301).

2⁶⁴⁷⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

647665 is a deficient number, since it is larger than the sum of its proper divisors (129539).

647665 is a wasteful number, since it uses less digits than its factorization.

647665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129538.

The product of its digits is 30240, while the sum is 34.

The square root of 647665 is about 804.7763664522. The cubic root of 647665 is about 86.5200594996.

The spelling of 647665 in words is "six hundred forty-seven thousand, six hundred sixty-five".