81021972 has 48 divisors (see below), whose sum is σ = 196019712. Its totient is φ = 26019840.

The previous prime is 81021959. The next prime is 81021973. The reversal of 81021972 is 27912018.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81021973) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 131008 + ... + 131624.

It is an arithmetic number, because the mean of its divisors is an integer number (4083744).

Almost surely, 2^81021972 is an apocalyptic number.

It is an amenable number.

81021972 is an abundant number, since it is smaller than the sum of its proper divisors (114997740).

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

81021972 is a wasteful number, since it uses less digits than its factorization.

81021972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1008 (or 1006 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 81021972 is about 9001.2205838986. The cubic root of 81021972 is about 432.7139899103.

The spelling of 81021972 in words is "eighty-one million, twenty-one thousand, nine hundred seventy-two".