668555905 has 16 divisors (see below), whose sum is σ = 808761744. Its totient is φ = 530530560.

The previous prime is 668555887. The next prime is 668555933. The reversal of 668555905 is 509555866.

668555905 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 8 ways, for example, as 47499664 + 621056241 = 6892^2 + 24921^2 .

It is not a de Polignac number, because 668555905 - 2¹⁵ = 668523137 is a prime.

It is a super-2 number, since 2×668555905² = 893933996220738050, which contains 22 as substring.

It is a Duffinian 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, 654295 + ... + 655315.

It is an arithmetic number, because the mean of its divisors is an integer number (50547609).

Almost surely, 2^668555905 is an apocalyptic number.

It is an amenable number.

668555905 is a deficient number, since it is larger than the sum of its proper divisors (140205839).

668555905 is a wasteful number, since it uses less digits than its factorization.

668555905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1956.

The product of its (nonzero) digits is 1620000, while the sum is 49.

The square root of 668555905 is about 25856.4480352581. The cubic root of 668555905 is about 874.4048873113.

The spelling of 668555905 in words is "six hundred sixty-eight million, five hundred fifty-five thousand, nine hundred five".