81791959 has 4 divisors (see below), whose sum is σ = 82152504. Its totient is φ = 81431416.

The previous prime is 81791953. The next prime is 81791987. The reversal of 81791959 is 95919718.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81791959 - 2³ = 81791951 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81791951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 179932 + ... + 180385.

It is an arithmetic number, because the mean of its divisors is an integer number (20538126).

Almost surely, 2^81791959 is an apocalyptic number.

81791959 is a deficient number, since it is larger than the sum of its proper divisors (360545).

81791959 is a wasteful number, since it uses less digits than its factorization.

81791959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360544.

The product of its digits is 204120, while the sum is 49.

The square root of 81791959 is about 9043.8907003568. The cubic root of 81791959 is about 434.0804267408.

The spelling of 81791959 in words is "eighty-one million, seven hundred ninety-one thousand, nine hundred fifty-nine".