645940 has 12 divisors (see below), whose sum is σ = 1356516. Its totient is φ = 258368.

The previous prime is 645937. The next prime is 645941. The reversal of 645940 is 49546.

It can be written as a sum of positive squares in 2 ways, for example, as 467856 + 178084 = 684^2 + 422^2 .

It is a junction number, because it is equal to n+sod(n) for n = 645899 and 645908.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645941) 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, 16129 + ... + 16168.

It is an arithmetic number, because the mean of its divisors is an integer number (113043).

2⁶⁴⁵⁹⁴⁰ is an apocalyptic number.

It is an amenable number.

645940 is an abundant number, since it is smaller than the sum of its proper divisors (710576).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

645940 is a wasteful number, since it uses less digits than its factorization.

645940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32306 (or 32304 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 645940 is about 803.7039255845. The cubic root of 645940 is about 86.4431782924.

The spelling of 645940 in words is "six hundred forty-five thousand, nine hundred forty".