664581 has 16 divisors (see below), whose sum is σ = 955584. Its totient is φ = 409344.

The previous prime is 664579. The next prime is 664583. The reversal of 664581 is 185466.

It is an interprime number because it is at equal distance from previous prime (664579) and next prime (664583).

It is not a de Polignac number, because 664581 - 2¹ = 664579 is a prime.

It is a super-2 number, since 2×664581² = 883335811122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664583) 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, 4155 + ... + 4311.

It is an arithmetic number, because the mean of its divisors is an integer number (59724).

2⁶⁶⁴⁵⁸¹ is an apocalyptic number.

664581 is the 471-st octagonal number.

It is an amenable number.

664581 is a deficient number, since it is larger than the sum of its proper divisors (291003).

664581 is a wasteful number, since it uses less digits than its factorization.

664581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 260.

The product of its digits is 5760, while the sum is 30.

The square root of 664581 is about 815.2183756516. The cubic root of 664581 is about 87.2668514234.

The spelling of 664581 in words is "six hundred sixty-four thousand, five hundred eighty-one".