81965520 has 400 divisors, whose sum is σ = 352894080. Its totient is φ = 17169408.

The previous prime is 81965479. The next prime is 81965557. The reversal of 81965520 is 2556918.

It is a happy number.

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 79 ways as a sum of consecutive naturals, for example, 589611 + ... + 589749.

Almost surely, 2^81965520 is an apocalyptic number.

81965520 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 81965520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (176447040).

81965520 is an abundant number, since it is smaller than the sum of its proper divisors (270928560).

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

81965520 is a wasteful number, since it uses less digits than its factorization.

81965520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184 (or 169 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 81965520 is about 9053.4810984505. The cubic root of 81965520 is about 434.3872466571.

The spelling of 81965520 in words is "eighty-one million, nine hundred sixty-five thousand, five hundred twenty".