81381672 has 48 divisors (see below), whose sum is σ = 228577440. Its totient is φ = 27126576.

The previous prime is 81381653. The next prime is 81381673. The reversal of 81381672 is 27618318.

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

It is not an unprimeable number, because it can be changed into a prime (81381673) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18988 + ... + 22875.

It is an arithmetic number, because the mean of its divisors is an integer number (4762030).

Almost surely, 2^81381672 is an apocalyptic number.

It is an amenable number.

81381672 is an abundant number, since it is smaller than the sum of its proper divisors (147195768).

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

81381672 is a wasteful number, since it uses less digits than its factorization.

81381672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41884 (or 41868 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 81381672 is about 9021.1790803642. The cubic root of 81381672 is about 433.3533944690.

The spelling of 81381672 in words is "eighty-one million, three hundred eighty-one thousand, six hundred seventy-two".