664905 has 16 divisors (see below), whose sum is σ = 1120320. Its totient is φ = 335808.

The previous prime is 664891. The next prime is 664933. The reversal of 664905 is 509466.

664905 = T₂₅₅ + T₂₅₆ + ... + T₂₇₃.

It is not a de Polignac number, because 664905 - 2⁷ = 664777 is a prime.

664905 is a lucky number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 882 + ... + 1451.

It is an arithmetic number, because the mean of its divisors is an integer number (70020).

2⁶⁶⁴⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

664905 is a deficient number, since it is larger than the sum of its proper divisors (455415).

664905 is a wasteful number, since it uses less digits than its factorization.

664905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2360.

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 664905 is about 815.4170711973. The cubic root of 664905 is about 87.2810307164.

The spelling of 664905 in words is "six hundred sixty-four thousand, nine hundred five".