665405 has 16 divisors (see below), whose sum is σ = 892080. Its totient is φ = 473088.

The previous prime is 665387. The next prime is 665419. The reversal of 665405 is 504566.

It can be written as a sum of positive squares in 8 ways, for example, as 58564 + 606841 = 242^2 + 779^2 .

It is a cyclic number.

It is not a de Polignac number, because 665405 - 2¹⁰ = 664381 is a prime.

It is a plaindrome in base 9 and base 14.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1709 + ... + 2061.

It is an arithmetic number, because the mean of its divisors is an integer number (55755).

2⁶⁶⁵⁴⁰⁵ is an apocalyptic number.

665405 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

665405 is a deficient number, since it is larger than the sum of its proper divisors (226675).

665405 is a wasteful number, since it uses less digits than its factorization.

665405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400.

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

The square root of 665405 is about 815.7236051507. The cubic root of 665405 is about 87.3029033052.

The spelling of 665405 in words is "six hundred sixty-five thousand, four hundred five".