1645591 has 4 divisors (see below), whose sum is σ = 1652112. Its totient is φ = 1639072.

The previous prime is 1645561. The next prime is 1645601. The reversal of 1645591 is 1955461.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1645591 - 2⁵ = 1645559 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

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 3 ways as a sum of consecutive naturals, for example, 2866 + ... + 3391.

It is an arithmetic number, because the mean of its divisors is an integer number (413028).

2^1645591 is an apocalyptic number.

1645591 is a deficient number, since it is larger than the sum of its proper divisors (6521).

1645591 is an equidigital number, since it uses as much as digits as its factorization.

1645591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6520.

The product of its digits is 5400, while the sum is 31.

The square root of 1645591 is about 1282.8059089356. The cubic root of 1645591 is about 118.0612293549.

The spelling of 1645591 in words is "one million, six hundred forty-five thousand, five hundred ninety-one".