1780645 has 4 divisors (see below), whose sum is σ = 2136780. Its totient is φ = 1424512.

The previous prime is 1780643. The next prime is 1780663. The reversal of 1780645 is 5460871.

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

It can be written as a sum of positive squares in 2 ways, for example, as 599076 + 1181569 = 774^2 + 1087^2 .

It is a cyclic number.

It is not a de Polignac number, because 1780645 - 2¹ = 1780643 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.

1780645 is a lucky number.

It is a plaindrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1780643) 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, 178060 + ... + 178069.

It is an arithmetic number, because the mean of its divisors is an integer number (534195).

2^1780645 is an apocalyptic number.

It is an amenable number.

1780645 is a deficient number, since it is larger than the sum of its proper divisors (356135).

1780645 is an equidigital number, since it uses as much as digits as its factorization.

1780645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 356134.

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 1780645 is about 1334.4081084886. The cubic root of 1780645 is about 121.2064639815.

The spelling of 1780645 in words is "one million, seven hundred eighty thousand, six hundred forty-five".