664651 has 16 divisors (see below), whose sum is σ = 776160. Its totient is φ = 564480.

The previous prime is 664633. The next prime is 664661. The reversal of 664651 is 156466.

It is a 8-Lehmer number, since φ(664651) divides (664651-1)⁸.

It is a cyclic number.

It is not a de Polignac number, because 664651 - 2⁵ = 664619 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664621) 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, 15436 + ... + 15478.

It is an arithmetic number, because the mean of its divisors is an integer number (48510).

2⁶⁶⁴⁶⁵¹ is an apocalyptic number.

664651 is a deficient number, since it is larger than the sum of its proper divisors (111509).

664651 is a wasteful number, since it uses less digits than its factorization.

664651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126.

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

The square root of 664651 is about 815.2613078026. The cubic root of 664651 is about 87.2699152411.

It can be divided in two parts, 66465 and 1, that added together give a palindrome (66466).

The spelling of 664651 in words is "six hundred sixty-four thousand, six hundred fifty-one".