81371520 has 256 divisors, whose sum is σ = 306244800. Its totient is φ = 20348928.

The previous prime is 81371519. The next prime is 81371527. The reversal of 81371520 is 2517318.

81371520 is a `hidden beast` number, since 8 + 137 + 1 + 520 = 666.

It is a super-2 number, since 2×81371520² = 13242648534220800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81371527) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 293622 + ... + 293898.

Almost surely, 2^81371520 is an apocalyptic number.

81371520 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 81371520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (153122400).

81371520 is an abundant number, since it is smaller than the sum of its proper divisors (224873280).

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

81371520 is a wasteful number, since it uses less digits than its factorization.

81371520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322 (or 304 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 81371520 is about 9020.6163869217. The cubic root of 81371520 is about 433.3353740864.

Adding to 81371520 its reverse (2517318), we get a palindrome (83888838).

The spelling of 81371520 in words is "eighty-one million, three hundred seventy-one thousand, five hundred twenty".