664551 has 16 divisors (see below), whose sum is σ = 997120. Its totient is φ = 437400.

The previous prime is 664549. The next prime is 664561. The reversal of 664551 is 155466.

It is a happy number.

It is not a de Polignac number, because 664551 - 2¹ = 664549 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664511) by changing a digit.

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, 3996 + ... + 4158.

It is an arithmetic number, because the mean of its divisors is an integer number (62320).

2⁶⁶⁴⁵⁵¹ is an apocalyptic number.

664551 is a deficient number, since it is larger than the sum of its proper divisors (332569).

664551 is a wasteful number, since it uses less digits than its factorization.

664551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323 (or 317 counting only the distinct ones).

The product of its digits is 3600, while the sum is 27.

The square root of 664551 is about 815.1999754661. The cubic root of 664551 is about 87.2655382928.

The spelling of 664551 in words is "six hundred sixty-four thousand, five hundred fifty-one".