71991881809957 has 2 divisors, whose sum is σ = 71991881809958. Its totient is φ = 71991881809956.

The previous prime is 71991881809907. The next prime is 71991881809963. The reversal of 71991881809957 is 75990818819917.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64109342662561 + 7882539147396 = 8006831^2 + 2807586^2 .

It is a cyclic number.

It is not a de Polignac number, because 71991881809957 - 2¹⁹ = 71991881285669 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71991881809907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35995940904978 + 35995940904979.

It is an arithmetic number, because the mean of its divisors is an integer number (35995940904979).

Almost surely, 2^{71991881809957} is an apocalyptic number.

It is an amenable number.

71991881809957 is a deficient number, since it is larger than the sum of its proper divisors (1).

71991881809957 is an equidigital number, since it uses as much as digits as its factorization.

71991881809957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 823011840, while the sum is 82.

The spelling of 71991881809957 in words is "seventy-one trillion, nine hundred ninety-one billion, eight hundred eighty-one million, eight hundred nine thousand, nine hundred fifty-seven".