81639888 has 40 divisors (see below), whose sum is σ = 230077536. Its totient is φ = 24739200.

The previous prime is 81639841. The next prime is 81639889. The reversal of 81639888 is 88893618.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 81639888.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81639889) 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, 76783 + ... + 77838.

Almost surely, 2^81639888 is an apocalyptic number.

81639888 is a gapful number since it is divisible by the number (88) formed by its first and last digit.

It is an amenable number.

81639888 is an abundant number, since it is smaller than the sum of its proper divisors (148437648).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81639888 is a wasteful number, since it uses less digits than its factorization.

81639888 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154643 (or 154637 counting only the distinct ones).

The product of its digits is 663552, while the sum is 51.

The square root of 81639888 is about 9035.4794006738. The cubic root of 81639888 is about 433.8112397373.

It can be divided in two parts, 816 and 39888, that added together give a palindrome (40704).

The spelling of 81639888 in words is "eighty-one million, six hundred thirty-nine thousand, eight hundred eighty-eight".