81333520 has 40 divisors (see below), whose sum is σ = 197326656. Its totient is φ = 31118208.

The previous prime is 81333517. The next prime is 81333529. The reversal of 81333520 is 2533318.

It is a tau number, because it is divible by the number of its divisors (40).

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (81333529) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20262 + ... + 23941.

Almost surely, 2^81333520 is an apocalyptic number.

81333520 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81333520 is an abundant number, since it is smaller than the sum of its proper divisors (115993136).

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

81333520 is a wasteful number, since it uses less digits than its factorization.

81333520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44239 (or 44233 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 25.

The square root of 81333520 is about 9018.5098547376. The cubic root of 81333520 is about 433.2679085973.

Adding to 81333520 its reverse (2533318), we get a palindrome (83866838).

The spelling of 81333520 in words is "eighty-one million, three hundred thirty-three thousand, five hundred twenty".