81638871 has 8 divisors (see below), whose sum is σ = 108906624. Its totient is φ = 54398520.

The previous prime is 81638867. The next prime is 81638881. The reversal of 81638871 is 17883618.

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

It is not a de Polignac number, because 81638871 - 2² = 81638867 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81638861) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1590 + ... + 12876.

It is an arithmetic number, because the mean of its divisors is an integer number (13613328).

Almost surely, 2^81638871 is an apocalyptic number.

81638871 is a deficient number, since it is larger than the sum of its proper divisors (27267753).

81638871 is a wasteful number, since it uses less digits than its factorization.

81638871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13701.

The product of its digits is 64512, while the sum is 42.

The square root of 81638871 is about 9035.4231223557. The cubic root of 81638871 is about 433.8094383799.

The spelling of 81638871 in words is "eighty-one million, six hundred thirty-eight thousand, eight hundred seventy-one".