71991000181 has 2 divisors, whose sum is σ = 71991000182. Its totient is φ = 71991000180.

The previous prime is 71991000041. The next prime is 71991000187. The reversal of 71991000181 is 18100019917.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 63084359556 + 8906640625 = 251166^2 + 94375^2 .

It is a cyclic number.

It is not a de Polignac number, because 71991000181 - 2²¹ = 71988903029 is a prime.

It is a super-2 number, since 2×71991000181² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 71991000181.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71991000187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35995500090 + 35995500091.

It is an arithmetic number, because the mean of its divisors is an integer number (35995500091).

Almost surely, 2^71991000181 is an apocalyptic number.

It is an amenable number.

71991000181 is a deficient number, since it is larger than the sum of its proper divisors (1).

71991000181 is an equidigital number, since it uses as much as digits as its factorization.

71991000181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 37.

The spelling of 71991000181 in words is "seventy-one billion, nine hundred ninety-one million, one hundred eighty-one", and thus it is an aban number.