645404 has 12 divisors (see below), whose sum is σ = 1153824. Its totient is φ = 315744.

The previous prime is 645397. The next prime is 645409. The reversal of 645404 is 404546.

645404 = T₆₇ + T₆₈ + ... + T₁₆₀.

It is a happy number.

645404 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 645404.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645404.

It is not an unprimeable number, because it can be changed into a prime (645409) by changing a digit.

645404 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1529 + ... + 1904.

It is an arithmetic number, because the mean of its divisors is an integer number (96152).

2⁶⁴⁵⁴⁰⁴ is an apocalyptic number.

It is an amenable number.

645404 is a deficient number, since it is larger than the sum of its proper divisors (508420).

645404 is a wasteful number, since it uses less digits than its factorization.

645404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3484 (or 3482 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 23.

The square root of 645404 is about 803.3704002513. The cubic root of 645404 is about 86.4192615378.

The spelling of 645404 in words is "six hundred forty-five thousand, four hundred four".