81970920 has 128 divisors (see below), whose sum is σ = 277344000. Its totient is φ = 21530880.

The previous prime is 81970891. The next prime is 81970927. The reversal of 81970920 is 2907918.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81970927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 76146 + ... + 77214.

It is an arithmetic number, because the mean of its divisors is an integer number (2166750).

Almost surely, 2^81970920 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 81970920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (138672000).

81970920 is an abundant number, since it is smaller than the sum of its proper divisors (195373080).

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

81970920 is a wasteful number, since it uses less digits than its factorization.

81970920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1160 (or 1150 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

The square root of 81970920 is about 9053.7793213663. The cubic root of 81970920 is about 434.3967857886.

The spelling of 81970920 in words is "eighty-one million, nine hundred seventy thousand, nine hundred twenty".