81881520 has 320 divisors, whose sum is σ = 318836736. Its totient is φ = 16957440.

The previous prime is 81881479. The next prime is 81881533. The reversal of 81881520 is 2518818.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1342290 + ... + 1342350.

Almost surely, 2^81881520 is an apocalyptic number.

81881520 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 81881520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (159418368).

81881520 is an abundant number, since it is smaller than the sum of its proper divisors (236955216).

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

81881520 is a wasteful number, since it uses less digits than its factorization.

81881520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148 (or 142 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 33.

The square root of 81881520 is about 9048.8408097391. The cubic root of 81881520 is about 434.2388061887.

The spelling of 81881520 in words is "eighty-one million, eight hundred eighty-one thousand, five hundred twenty".