665540 has 24 divisors (see below), whose sum is σ = 1415232. Its totient is φ = 262880.

The previous prime is 665527. The next prime is 665549. The reversal of 665540 is 45566.

It is a plaindrome in base 14.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (665549) 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, 1985 + ... + 2295.

It is an arithmetic number, because the mean of its divisors is an integer number (58968).

2⁶⁶⁵⁵⁴⁰ is an apocalyptic number.

It is an amenable number.

665540 is an abundant number, since it is smaller than the sum of its proper divisors (749692).

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

665540 is a wasteful number, since it uses less digits than its factorization.

665540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 427 (or 425 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 665540 is about 815.8063495708. The cubic root of 665540 is about 87.3088070255.

Adding to 665540 its sum of digits (26), we get a palindrome (665566).

The spelling of 665540 in words is "six hundred sixty-five thousand, five hundred forty".