81169920 has 240 divisors, whose sum is σ = 303855552. Its totient is φ = 19906560.

The previous prime is 81169909. The next prime is 81169961. The reversal of 81169920 is 2996118.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 299385 + ... + 299655.

Almost surely, 2^81169920 is an apocalyptic number.

81169920 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 81169920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (151927776).

81169920 is an abundant number, since it is smaller than the sum of its proper divisors (222685632).

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

81169920 is a wasteful number, since it uses less digits than its factorization.

81169920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 313 (or 294 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 81169920 is about 9009.4350544304. The cubic root of 81169920 is about 432.9772116861.

The spelling of 81169920 in words is "eighty-one million, one hundred sixty-nine thousand, nine hundred twenty".