668405 has 8 divisors (see below), whose sum is σ = 823992. Its totient is φ = 520128.

The previous prime is 668347. The next prime is 668407. The reversal of 668405 is 504866.

668405 = T₂₉₁ + T₂₉₂ + ... + T₃₀₅.

It can be written as a sum of positive squares in 4 ways, for example, as 18769 + 649636 = 137^2 + 806^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-668405 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668407) 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 7 ways as a sum of consecutive naturals, for example, 1622 + ... + 1991.

It is an arithmetic number, because the mean of its divisors is an integer number (102999).

2⁶⁶⁸⁴⁰⁵ is an apocalyptic number.

It is an amenable number.

668405 is a deficient number, since it is larger than the sum of its proper divisors (155587).

668405 is a wasteful number, since it uses less digits than its factorization.

668405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3655.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 668405 is about 817.5603953226. The cubic root of 668405 is about 87.4339092764.

The spelling of 668405 in words is "six hundred sixty-eight thousand, four hundred five".