81081972 has 30 divisors (see below), whose sum is σ = 211965138. Its totient is φ = 27027216.

The previous prime is 81081919. The next prime is 81081977. The reversal of 81081972 is 27918018.

It can be written as a sum of positive squares in only one way, i.e., 47279376 + 33802596 = 6876^2 + 5814^2 .

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 (81081977) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 124803 + ... + 125450.

Almost surely, 2^81081972 is an apocalyptic number.

It is an amenable number.

81081972 is an abundant number, since it is smaller than the sum of its proper divisors (130883166).

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

81081972 is a wasteful number, since it uses less digits than its factorization.

81081972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 250269 (or 250258 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 81081972 is about 9004.5528484206. The cubic root of 81081972 is about 432.8207775407.

The spelling of 81081972 in words is "eighty-one million, eighty-one thousand, nine hundred seventy-two".