81688000 has 56 divisors (see below), whose sum is σ = 202320144. Its totient is φ = 32672000.

The previous prime is 81687997. The next prime is 81688073. The reversal of 81688000 is 88618.

81688000 = 267² + 268² + ... + 641².

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2895 + ... + 13105.

Almost surely, 2^81688000 is an apocalyptic number.

81688000 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81688000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (101160072).

81688000 is an abundant number, since it is smaller than the sum of its proper divisors (120632144).

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

81688000 is a wasteful number, since it uses less digits than its factorization.

81688000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10238 (or 10218 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 31.

The square root of 81688000 is about 9038.1414018591. The cubic root of 81688000 is about 433.8964408493.

The spelling of 81688000 in words is "eighty-one million, six hundred eighty-eight thousand".