81972660 has 144 divisors (see below), whose sum is σ = 288505728. Its totient is φ = 17022720.

The previous prime is 81972643. The next prime is 81972661. The reversal of 81972660 is 6627918.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81972661) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 50014 + ... + 51626.

It is an arithmetic number, because the mean of its divisors is an integer number (2003512).

Almost surely, 2^81972660 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 81972660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144252864).

81972660 is an abundant number, since it is smaller than the sum of its proper divisors (206533068).

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

81972660 is a wasteful number, since it uses less digits than its factorization.

81972660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1654 (or 1641 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 39.

The square root of 81972660 is about 9053.8754133244. The cubic root of 81972660 is about 434.3998594195.

The spelling of 81972660 in words is "eighty-one million, nine hundred seventy-two thousand, six hundred sixty".