81505944 has 144 divisors (see below), whose sum is σ = 250111680. Its totient is φ = 23811840.

The previous prime is 81505937. The next prime is 81505961. The reversal of 81505944 is 44950518.

It is a super-2 number, since 2×81505944² = 13286437814662272, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81505899 and 81505908.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1537822 + ... + 1537874.

Almost surely, 2^81505944 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 81505944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (125055840).

81505944 is an abundant number, since it is smaller than the sum of its proper divisors (168605736).

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

81505944 is a wasteful number, since it uses less digits than its factorization.

81505944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162 (or 102 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 36.

The square root of 81505944 is about 9028.0642443439. The cubic root of 81505944 is about 433.5738630460.

The spelling of 81505944 in words is "eighty-one million, five hundred five thousand, nine hundred forty-four".