645778 has 16 divisors (see below), whose sum is σ = 1117440. Its totient is φ = 274176.

The previous prime is 645763. The next prime is 645787. The reversal of 645778 is 877546.

It is a happy number.

645778 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2583 + ... + 2821.

It is an arithmetic number, because the mean of its divisors is an integer number (69840).

2⁶⁴⁵⁷⁷⁸ is an apocalyptic number.

645778 is a deficient number, since it is larger than the sum of its proper divisors (471662).

645778 is a wasteful number, since it uses less digits than its factorization.

645778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 441.

The product of its digits is 47040, while the sum is 37.

The square root of 645778 is about 803.6031358824. The cubic root of 645778 is about 86.4359511166.

The spelling of 645778 in words is "six hundred forty-five thousand, seven hundred seventy-eight".