81638879 has 8 divisors (see below), whose sum is σ = 98790048. Its totient is φ = 65859840.

The previous prime is 81638867. The next prime is 81638881. The reversal of 81638879 is 97883618.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81638879 - 2⁴ = 81638863 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81634879) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 342902 + ... + 343139.

It is an arithmetic number, because the mean of its divisors is an integer number (12348756).

Almost surely, 2^81638879 is an apocalyptic number.

81638879 is a deficient number, since it is larger than the sum of its proper divisors (17151169).

81638879 is a wasteful number, since it uses less digits than its factorization.

81638879 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 686065.

The product of its digits is 580608, while the sum is 50.

The square root of 81638879 is about 9035.4235650577. The cubic root of 81638879 is about 433.8094525499.

The spelling of 81638879 in words is "eighty-one million, six hundred thirty-eight thousand, eight hundred seventy-nine".