76691981 has 4 divisors (see below), whose sum is σ = 81203292. Its totient is φ = 72180672.

The previous prime is 76691969. The next prime is 76691987. The reversal of 76691981 is 18919667.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18919667 = 13 ⋅1455359.

It can be written as a sum of positive squares in 2 ways, for example, as 31922500 + 44769481 = 5650^2 + 6691^2 .

It is a cyclic number.

It is not a de Polignac number, because 76691981 - 2²⁶ = 9583117 is a prime.

It is a super-3 number, since 3×76691981³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (76691987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2255630 + ... + 2255663.

It is an arithmetic number, because the mean of its divisors is an integer number (20300823).

Almost surely, 2^76691981 is an apocalyptic number.

It is an amenable number.

76691981 is a deficient number, since it is larger than the sum of its proper divisors (4511311).

76691981 is a wasteful number, since it uses less digits than its factorization.

76691981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4511310.

The product of its digits is 163296, while the sum is 47.

The square root of 76691981 is about 8757.3957887034. The cubic root of 76691981 is about 424.8640506347.

The spelling of 76691981 in words is "seventy-six million, six hundred ninety-one thousand, nine hundred eighty-one".