81005000 has 80 divisors (see below), whose sum is σ = 201169980. Its totient is φ = 30464000.

The previous prime is 81004993. The next prime is 81005009. The reversal of 81005000 is 50018.

It can be written as a sum of positive squares in 10 ways, for example, as 2540836 + 78464164 = 1594^2 + 8858^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81005009) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 84524 + ... + 85476.

Almost surely, 2^81005000 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 81005000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100584990).

81005000 is an abundant number, since it is smaller than the sum of its proper divisors (120164980).

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

81005000 is a wasteful number, since it uses less digits than its factorization.

81005000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 996 (or 977 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 81005000 is about 9000.2777734912. The cubic root of 81005000 is about 432.6837736842.

Adding to 81005000 its reverse (50018), we get a palindrome (81055018).

The spelling of 81005000 in words is "eighty-one million, five thousand".