1645904 has 40 divisors (see below), whose sum is σ = 3536232. Its totient is φ = 737280.

The previous prime is 1645901. The next prime is 1645907. The reversal of 1645904 is 4095461.

It is an interprime number because it is at equal distance from previous prime (1645901) and next prime (1645907).

It can be written as a sum of positive squares in 4 ways, for example, as 78400 + 1567504 = 280^2 + 1252^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1645901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8432 + ... + 8624.

2^1645904 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1645904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1768116).

1645904 is an abundant number, since it is smaller than the sum of its proper divisors (1890328).

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

1645904 is a wasteful number, since it uses less digits than its factorization.

1645904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 255 (or 249 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 1645904 is about 1282.9279013257. The cubic root of 1645904 is about 118.0687141678.

It can be divided in two parts, 164 and 5904, that multiplied together give a square (968256 = 984²).

The spelling of 1645904 in words is "one million, six hundred forty-five thousand, nine hundred four".