667181681 has 2 divisors, whose sum is σ = 667181682. Its totient is φ = 667181680.

The previous prime is 667181663. The next prime is 667181693. The reversal of 667181681 is 186181766.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 625450081 + 41731600 = 25009^2 + 6460^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-667181681 is a prime.

It is a super-2 number, since 2×667181681² = 890262790923971522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (667181651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333590840 + 333590841.

It is an arithmetic number, because the mean of its divisors is an integer number (333590841).

Almost surely, 2^667181681 is an apocalyptic number.

It is an amenable number.

667181681 is a deficient number, since it is larger than the sum of its proper divisors (1).

667181681 is an equidigital number, since it uses as much as digits as its factorization.

667181681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96768, while the sum is 44.

The square root of 667181681 is about 25829.8602590103. The cubic root of 667181681 is about 873.8053600644.

The spelling of 667181681 in words is "six hundred sixty-seven million, one hundred eighty-one thousand, six hundred eighty-one".