81049920 has 168 divisors, whose sum is σ = 299520864. Its totient is φ = 18514944.

The previous prime is 81049889. The next prime is 81049921. The reversal of 81049920 is 2994018.

It is a tau number, because it is divible by the number of its divisors (168).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81049921) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 46179 + ... + 47901.

Almost surely, 2^81049920 is an apocalyptic number.

81049920 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81049920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149760432).

81049920 is an abundant number, since it is smaller than the sum of its proper divisors (218470944).

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

81049920 is a wasteful number, since it uses less digits than its factorization.

81049920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1757 (or 1740 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 81049920 is about 9002.7729061662. The cubic root of 81049920 is about 432.7637381454.

The spelling of 81049920 in words is "eighty-one million, forty-nine thousand, nine hundred twenty".