81689472 has 80 divisors (see below), whose sum is σ = 243137400. Its totient is φ = 27226368.

The previous prime is 81689467. The next prime is 81689473. The reversal of 81689472 is 27498618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81689473) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 6429 + ... + 14307.

Almost surely, 2^81689472 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 81689472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (121568700).

81689472 is an abundant number, since it is smaller than the sum of its proper divisors (161447928).

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

81689472 is an equidigital number, since it uses as much as digits as its factorization.

81689472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7905 (or 7884 counting only the distinct ones).

The product of its digits is 193536, while the sum is 45.

The square root of 81689472 is about 9038.2228341638. Note that the first 3 decimals coincide. The cubic root of 81689472 is about 433.8990470735.

The spelling of 81689472 in words is "eighty-one million, six hundred eighty-nine thousand, four hundred seventy-two".