664665 has 16 divisors (see below), whose sum is σ = 1079808. Its totient is φ = 349056.

The previous prime is 664663. The next prime is 664667. The reversal of 664665 is 566466.

It is an interprime number because it is at equal distance from previous prime (664663) and next prime (664667).

It is not a de Polignac number, because 664665 - 2¹ = 664663 is a prime.

664665 is a lucky number.

It is a plaindrome in base 9.

It is not an unprimeable number, because it can be changed into a prime (664661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 792 + ... + 1398.

It is an arithmetic number, because the mean of its divisors is an integer number (67488).

2⁶⁶⁴⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

664665 is a deficient number, since it is larger than the sum of its proper divisors (415143).

664665 is a wasteful number, since it uses less digits than its factorization.

664665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 688.

The product of its digits is 25920, while the sum is 33.

The square root of 664665 is about 815.2698939615. The cubic root of 664665 is about 87.2705279788.

The spelling of 664665 in words is "six hundred sixty-four thousand, six hundred sixty-five".