71666981 has 2 divisors, whose sum is σ = 71666982. Its totient is φ = 71666980.

The previous prime is 71666977. The next prime is 71666999. The reversal of 71666981 is 18966617.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69989956 + 1677025 = 8366^2 + 1295^2 .

It is a cyclic number.

It is not a de Polignac number, because 71666981 - 2² = 71666977 is a prime.

It is a super-2 number, since 2×71666981² = 10272312331308722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71666941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35833490 + 35833491.

It is an arithmetic number, because the mean of its divisors is an integer number (35833491).

Almost surely, 2^71666981 is an apocalyptic number.

It is an amenable number.

71666981 is a deficient number, since it is larger than the sum of its proper divisors (1).

71666981 is an equidigital number, since it uses as much as digits as its factorization.

71666981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 44.

The square root of 71666981 is about 8465.6352980742. The cubic root of 71666981 is about 415.3743774138.

The spelling of 71666981 in words is "seventy-one million, six hundred sixty-six thousand, nine hundred eighty-one".