71661661 has 2 divisors, whose sum is σ = 71661662. Its totient is φ = 71661660.

The previous prime is 71661599. The next prime is 71661679. The reversal of 71661661 is 16616617.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64802500 + 6859161 = 8050^2 + 2619^2 .

It is an emirp because it is prime and its reverse (16616617) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 71661661 - 2⁷ = 71661533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71661361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35830830 + 35830831.

It is an arithmetic number, because the mean of its divisors is an integer number (35830831).

Almost surely, 2^71661661 is an apocalyptic number.

It is an amenable number.

71661661 is a deficient number, since it is larger than the sum of its proper divisors (1).

71661661 is an equidigital number, since it uses as much as digits as its factorization.

71661661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 34.

The square root of 71661661 is about 8465.3210807388. The cubic root of 71661661 is about 415.3640991036.

The spelling of 71661661 in words is "seventy-one million, six hundred sixty-one thousand, six hundred sixty-one".