81972900 has 54 divisors (see below), whose sum is σ = 256942322. Its totient is φ = 21859200.

The previous prime is 81972883. The next prime is 81972901. The reversal of 81972900 is 927918.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 11009124 + 70963776 = 3318^2 + 8424^2 .

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 (81972901) 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 17 ways as a sum of consecutive naturals, for example, 44641 + ... + 46440.

Almost surely, 2^81972900 is an apocalyptic number.

It is an amenable number.

81972900 is an abundant number, since it is smaller than the sum of its proper divisors (174969422).

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

81972900 is a wasteful number, since it uses less digits than its factorization.

81972900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91101 (or 91091 counting only the distinct ones).

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

The square root of 81972900 is about 9053.8886673075. Note that the first 3 decimals coincide. The cubic root of 81972900 is about 434.4002833652.

The spelling of 81972900 in words is "eighty-one million, nine hundred seventy-two thousand, nine hundred".