81400072 has 32 divisors (see below), whose sum is σ = 166080600. Its totient is φ = 37177344.

The previous prime is 81400031. The next prime is 81400073. The reversal of 81400072 is 27000418.

It can be written as a sum of positive squares in 4 ways, for example, as 25060036 + 56340036 = 5006^2 + 7506^2 .

It is not an unprimeable number, because it can be changed into a prime (81400073) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6054 + ... + 14122.

Almost surely, 2^81400072 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 81400072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (83040300).

81400072 is an abundant number, since it is smaller than the sum of its proper divisors (84680528).

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

81400072 is a wasteful number, since it uses less digits than its factorization.

81400072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8185 (or 8181 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 81400072 is about 9022.1988450710. The cubic root of 81400072 is about 433.3860517058.

The spelling of 81400072 in words is "eighty-one million, four hundred thousand, seventy-two".