1665640 has 16 divisors (see below), whose sum is σ = 3747780. Its totient is φ = 666240.

The previous prime is 1665623. The next prime is 1665647. The reversal of 1665640 is 465661.

It can be written as a sum of positive squares in 2 ways, for example, as 1522756 + 142884 = 1234^2 + 378^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1665599 and 1665608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665647) 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, 20781 + ... + 20860.

2^1665640 is an apocalyptic number.

1665640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1665640 is an abundant number, since it is smaller than the sum of its proper divisors (2082140).

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

1665640 is a wasteful number, since it uses less digits than its factorization.

1665640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41652 (or 41648 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 1665640 is about 1290.5967611923. The cubic root of 1665640 is about 118.5387601905.

It can be divided in two parts, 16 and 65640, that added together give a palindrome (65656).

The spelling of 1665640 in words is "one million, six hundred sixty-five thousand, six hundred forty".