646945 has 16 divisors (see below), whose sum is σ = 861840. Its totient is φ = 463104.

The previous prime is 646937. The next prime is 646957. The reversal of 646945 is 549646.

It can be written as a sum of positive squares in 8 ways, for example, as 57121 + 589824 = 239^2 + 768^2 .

It is a cyclic number.

It is not a de Polignac number, because 646945 - 2³ = 646937 is a prime.

Its product of digits (25920) is a multiple of the sum of its prime divisors (324).

It is a self number, because there is not a number n which added to its sum of digits gives 646945.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 2271 + ... + 2539.

It is an arithmetic number, because the mean of its divisors is an integer number (53865).

2⁶⁴⁶⁹⁴⁵ is an apocalyptic number.

646945 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

646945 is a deficient number, since it is larger than the sum of its proper divisors (214895).

646945 is a wasteful number, since it uses less digits than its factorization.

646945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 324.

The product of its digits is 25920, while the sum is 34.

The square root of 646945 is about 804.3289128211. The cubic root of 646945 is about 86.4879865704.

The spelling of 646945 in words is "six hundred forty-six thousand, nine hundred forty-five".