668691505 has 4 divisors (see below), whose sum is σ = 802429812. Its totient is φ = 534953200.

The previous prime is 668691503. The next prime is 668691511. The reversal of 668691505 is 505196866.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 447068736 + 221622769 = 21144^2 + 14887^2 .

It is not a de Polignac number, because 668691505 - 2¹ = 668691503 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668691503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66869146 + ... + 66869155.

It is an arithmetic number, because the mean of its divisors is an integer number (200607453).

Almost surely, 2^668691505 is an apocalyptic number.

It is an amenable number.

668691505 is a deficient number, since it is larger than the sum of its proper divisors (133738307).

668691505 is a wasteful number, since it uses less digits than its factorization.

668691505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133738306.

The product of its (nonzero) digits is 388800, while the sum is 46.

The square root of 668691505 is about 25859.0700722203. The cubic root of 668691505 is about 874.4640004368.

The spelling of 668691505 in words is "six hundred sixty-eight million, six hundred ninety-one thousand, five hundred five".