81687744 has 112 divisors (see below), whose sum is σ = 246217440. Its totient is φ = 26542080.

The previous prime is 81687733. The next prime is 81687763. The reversal of 81687744 is 44778618.

It is a self number, because there is not a number n which added to its sum of digits gives 81687744.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 70272 + ... + 71424.

It is an arithmetic number, because the mean of its divisors is an integer number (2198370).

Almost surely, 2^81687744 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 81687744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (123108720).

81687744 is an abundant number, since it is smaller than the sum of its proper divisors (164529696).

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

81687744 is a wasteful number, since it uses less digits than its factorization.

81687744 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1215 (or 1199 counting only the distinct ones).

The product of its digits is 301056, while the sum is 45.

The square root of 81687744 is about 9038.1272396443. The cubic root of 81687744 is about 433.8959875897.

The spelling of 81687744 in words is "eighty-one million, six hundred eighty-seven thousand, seven hundred forty-four".