668216881 has 2 divisors, whose sum is σ = 668216882. Its totient is φ = 668216880.

The previous prime is 668216867. The next prime is 668216891. The reversal of 668216881 is 188612866.

668216881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 611078400 + 57138481 = 24720^2 + 7559^2 .

It is a cyclic number.

It is not a de Polignac number, because 668216881 - 2⁵ = 668216849 is a prime.

It is a super-2 number, since 2×668216881² = 893027600106736322, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (668216821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334108440 + 334108441.

It is an arithmetic number, because the mean of its divisors is an integer number (334108441).

Almost surely, 2^668216881 is an apocalyptic number.

It is an amenable number.

668216881 is a deficient number, since it is larger than the sum of its proper divisors (1).

668216881 is an equidigital number, since it uses as much as digits as its factorization.

668216881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 221184, while the sum is 46.

The square root of 668216881 is about 25849.8913150520. The cubic root of 668216881 is about 874.2570590528.

The spelling of 668216881 in words is "six hundred sixty-eight million, two hundred sixteen thousand, eight hundred eighty-one".