81687500 has 42 divisors (see below), whose sum is σ = 178825836. Its totient is φ = 32650000.

The previous prime is 81687439. The next prime is 81687503. The reversal of 81687500 is 578618.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (81687503) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 61847 + ... + 63153.

It is an arithmetic number, because the mean of its divisors is an integer number (4257758).

Almost surely, 2^81687500 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81687500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89412918).

81687500 is an abundant number, since it is smaller than the sum of its proper divisors (97138336).

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

81687500 is an equidigital number, since it uses as much as digits as its factorization.

81687500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1341 (or 1314 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 35.

The square root of 81687500 is about 9038.1137412626. The cubic root of 81687500 is about 433.8955555758.

The spelling of 81687500 in words is "eighty-one million, six hundred eighty-seven thousand, five hundred".