81291000 has 256 divisors, whose sum is σ = 299520000. Its totient is φ = 18345600.

The previous prime is 81290981. The next prime is 81291011. The reversal of 81291000 is 19218.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1028961 + ... + 1029039.

It is an arithmetic number, because the mean of its divisors is an integer number (1170000).

Almost surely, 2^81291000 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 81291000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149760000).

81291000 is an abundant number, since it is smaller than the sum of its proper divisors (218229000).

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

81291000 is a wasteful number, since it uses less digits than its factorization.

81291000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124 (or 96 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 81291000 is about 9016.1521726289. The cubic root of 81291000 is about 433.1923933495.

The spelling of 81291000 in words is "eighty-one million, two hundred ninety-one thousand".