668138671 has 2 divisors, whose sum is σ = 668138672. Its totient is φ = 668138670.

The previous prime is 668138663. The next prime is 668138683. The reversal of 668138671 is 176831866.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 668138671 - 2³ = 668138663 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668138651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334069335 + 334069336.

It is an arithmetic number, because the mean of its divisors is an integer number (334069336).

Almost surely, 2^668138671 is an apocalyptic number.

668138671 is a deficient number, since it is larger than the sum of its proper divisors (1).

668138671 is an equidigital number, since it uses as much as digits as its factorization.

668138671 is an evil number, because the sum of its binary digits is even.

The product of its digits is 290304, while the sum is 46.

The square root of 668138671 is about 25848.3784984668. The cubic root of 668138671 is about 874.2229492129. Note that the first 3 decimals are identical.

The spelling of 668138671 in words is "six hundred sixty-eight million, one hundred thirty-eight thousand, six hundred seventy-one".