81000072 has 24 divisors (see below), whose sum is σ = 219375390. Its totient is φ = 27000000.

The previous prime is 81000071. The next prime is 81000077. The reversal of 81000072 is 27000018.

It can be written as a sum of positive squares in only one way, i.e., 71673156 + 9326916 = 8466^2 + 3054^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is a super-2 number, since 2×81000072² = 13122023328010368, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (81000071) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 562429 + ... + 562572.

Almost surely, 2^81000072 is an apocalyptic number.

It is an amenable number.

81000072 is an abundant number, since it is smaller than the sum of its proper divisors (138375318).

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

81000072 is a wasteful number, since it uses less digits than its factorization.

81000072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1125013 (or 1125006 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 81000072 is about 9000.0039999991. The cubic root of 81000072 is about 432.6749992921.

The spelling of 81000072 in words is "eighty-one million, seventy-two", and thus it is an aban number and an uban number.