71216681 has 2 divisors, whose sum is σ = 71216682. Its totient is φ = 71216680.

The previous prime is 71216627. The next prime is 71216687. The reversal of 71216681 is 18661217.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58003456 + 13213225 = 7616^2 + 3635^2 .

It is an emirp because it is prime and its reverse (18661217) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 71216681 - 2¹⁰ = 71215657 is a prime.

It is a super-2 number, since 2×71216681² = 10143631305311522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (71216687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35608340 + 35608341.

It is an arithmetic number, because the mean of its divisors is an integer number (35608341).

Almost surely, 2^71216681 is an apocalyptic number.

It is an amenable number.

71216681 is a deficient number, since it is larger than the sum of its proper divisors (1).

71216681 is an equidigital number, since it uses as much as digits as its factorization.

71216681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4032, while the sum is 32.

The square root of 71216681 is about 8438.9976300506. The cubic root of 71216681 is about 414.5025849577.

Adding to 71216681 its reverse (18661217), we get a palindrome (89877898).

The spelling of 71216681 in words is "seventy-one million, two hundred sixteen thousand, six hundred eighty-one".