81081920 has 28 divisors (see below), whose sum is σ = 193077084. Its totient is φ = 32432640.

The previous prime is 81081919. The next prime is 81081977. The reversal of 81081920 is 2918018.

It can be written as a sum of positive squares in 2 ways, for example, as 24049216 + 57032704 = 4904^2 + 7552^2 .

It is a hoax number, since the sum of its digits (29) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 126371 + ... + 127010.

Almost surely, 2^81081920 is an apocalyptic number.

81081920 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81081920 is an abundant number, since it is smaller than the sum of its proper divisors (111995164).

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

81081920 is a wasteful number, since it uses less digits than its factorization.

81081920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 253398 (or 253388 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 81081920 is about 9004.5499609919. The cubic root of 81081920 is about 432.8206850142.

Adding to 81081920 its reverse (2918018), we get a palindrome (83999938).

The spelling of 81081920 in words is "eighty-one million, eighty-one thousand, nine hundred twenty".