71165981 has 4 divisors (see below), whose sum is σ = 71183964. Its totient is φ = 71148000.

The previous prime is 71165957. The next prime is 71166019. The reversal of 71165981 is 18956117.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18956117 = 23 ⋅824179.

It can be written as a sum of positive squares in 2 ways, for example, as 67798756 + 3367225 = 8234^2 + 1835^2 .

It is a cyclic number.

It is not a de Polignac number, because 71165981 - 2²⁶ = 4057117 is a prime.

It is a super-2 number, since 2×71165981² = 10129193703384722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71165581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 170 + ... + 11931.

It is an arithmetic number, because the mean of its divisors is an integer number (17795991).

Almost surely, 2^71165981 is an apocalyptic number.

It is an amenable number.

71165981 is a deficient number, since it is larger than the sum of its proper divisors (17983).

71165981 is a wasteful number, since it uses less digits than its factorization.

71165981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17982.

The product of its digits is 15120, while the sum is 38.

The square root of 71165981 is about 8435.9931839707. The cubic root of 71165981 is about 414.4041985041.

The spelling of 71165981 in words is "seventy-one million, one hundred sixty-five thousand, nine hundred eighty-one".