81687788 has 96 divisors (see below), whose sum is σ = 191245824. Its totient is φ = 29611008.

The previous prime is 81687779. The next prime is 81687791. The reversal of 81687788 is 88778618.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 265931 + ... + 266237.

It is an arithmetic number, because the mean of its divisors is an integer number (1992144).

Almost surely, 2^81687788 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 81687788, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95622912).

81687788 is an abundant number, since it is smaller than the sum of its proper divisors (109558036).

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

81687788 is a wasteful number, since it uses less digits than its factorization.

81687788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 391 (or 389 counting only the distinct ones).

The product of its digits is 1204224, while the sum is 53.

The square root of 81687788 is about 9038.1296737765. The cubic root of 81687788 is about 433.8960654937.

The spelling of 81687788 in words is "eighty-one million, six hundred eighty-seven thousand, seven hundred eighty-eight".