668687881 has 9 divisors (see below), whose sum is σ = 706253223. Its totient is φ = 633028320.

The previous prime is 668687827. The next prime is 668687927. The reversal of 668687881 is 188786866.

The square root of 668687881 is 25859.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 113614281 + 555073600 = 10659^2 + 23560^2 .

It is not a de Polignac number, because 668687881 - 2¹⁷ = 668556809 is a prime.

It is a super-2 number, since 2×668687881² = 894286964392540322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668687801) 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 8 ways as a sum of consecutive naturals, for example, 490641 + ... + 492001.

Almost surely, 2^668687881 is an apocalyptic number.

668687881 is the 25859-th square number.

668687881 is the 12930-th centered octagonal number.

It is an amenable number.

668687881 is a deficient number, since it is larger than the sum of its proper divisors (37565342).

668687881 is an frugal number, since it uses more digits than its factorization.

668687881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2760 (or 1380 counting only the distinct ones).

The product of its digits is 6193152, while the sum is 58.

The cubic root of 668687881 is about 874.4624207032.

The spelling of 668687881 in words is "six hundred sixty-eight million, six hundred eighty-seven thousand, eight hundred eighty-one".