81958931 has 4 divisors (see below), whose sum is σ = 82946472. Its totient is φ = 80971392.

The previous prime is 81958907. The next prime is 81958937. The reversal of 81958931 is 13985918.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13985918 = 2 ⋅6992959.

It is a cyclic number.

It is not a de Polignac number, because 81958931 - 2¹⁴ = 81942547 is a prime.

It is a super-2 number, since 2×81958931² = 13434532741325522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81958937) 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, 493646 + ... + 493811.

It is an arithmetic number, because the mean of its divisors is an integer number (20736618).

Almost surely, 2^81958931 is an apocalyptic number.

81958931 is a deficient number, since it is larger than the sum of its proper divisors (987541).

81958931 is an equidigital number, since it uses as much as digits as its factorization.

81958931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 987540.

The product of its digits is 77760, while the sum is 44.

The square root of 81958931 is about 9053.1171979600. The cubic root of 81958931 is about 434.3756065827.

The spelling of 81958931 in words is "eighty-one million, nine hundred fifty-eight thousand, nine hundred thirty-one".