81001836 has 48 divisors (see below), whose sum is σ = 211438080. Its totient is φ = 26816400.

The previous prime is 81001831. The next prime is 81001871. The reversal of 81001836 is 63810018.

It is a super-2 number, since 2×81001836² = 13122594870741792, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (81001831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13825 + ... + 18791.

It is an arithmetic number, because the mean of its divisors is an integer number (4404960).

Almost surely, 2^81001836 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 81001836, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105719040).

81001836 is an abundant number, since it is smaller than the sum of its proper divisors (130436244).

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

81001836 is a wasteful number, since it uses less digits than its factorization.

81001836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5131 (or 5123 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 81001836 is about 9000.1019994220. The cubic root of 81001836 is about 432.6781401665.

The spelling of 81001836 in words is "eighty-one million, one thousand, eight hundred thirty-six".