81929520 has 240 divisors, whose sum is σ = 297704160. Its totient is φ = 20127744.

The previous prime is 81929509. The next prime is 81929569. The reversal of 81929520 is 2592918.

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

It is a super-3 number, since 3×81929520³ (a number of 25 digits) contains 333 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 724984 + ... + 725096.

It is an arithmetic number, because the mean of its divisors is an integer number (1240434).

Almost surely, 2^81929520 is an apocalyptic number.

81929520 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 81929520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (148852080).

81929520 is an abundant number, since it is smaller than the sum of its proper divisors (215774640).

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

81929520 is a wasteful number, since it uses less digits than its factorization.

81929520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 204 (or 195 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 81929520 is about 9051.4926945781. The cubic root of 81929520 is about 434.3236417377.

The spelling of 81929520 in words is "eighty-one million, nine hundred twenty-nine thousand, five hundred twenty".