1645566 has 48 divisors (see below), whose sum is σ = 3816624. Its totient is φ = 470016.

The previous prime is 1645561. The next prime is 1645601. The reversal of 1645566 is 6655461.

Its product of digits (21600) is a multiple of the sum of its prime divisors (108).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1645561) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 22506 + ... + 22578.

It is an arithmetic number, because the mean of its divisors is an integer number (79513).

2^1645566 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1645566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1908312).

1645566 is an abundant number, since it is smaller than the sum of its proper divisors (2171058).

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

1645566 is a wasteful number, since it uses less digits than its factorization.

1645566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 125 (or 108 counting only the distinct ones).

The product of its digits is 21600, while the sum is 33.

The square root of 1645566 is about 1282.7961646341. The cubic root of 1645566 is about 118.0606314855.

It can be divided in two parts, 1645 and 566, that added together give a triangular number (2211 = T₆₆).

The spelling of 1645566 in words is "one million, six hundred forty-five thousand, five hundred sixty-six".