91281720 has 64 divisors (see below), whose sum is σ = 275490720. Its totient is φ = 24195584.

The previous prime is 91281713. The next prime is 91281731. The reversal of 91281720 is 2718219.

It is a super-3 number, since 3×91281720³ (a number of 25 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18562 + ... + 22958.

Almost surely, 2^91281720 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91281720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (137745360).

91281720 is an abundant number, since it is smaller than the sum of its proper divisors (184209000).

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

91281720 is a wasteful number, since it uses less digits than its factorization.

91281720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4584 (or 4580 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 91281720 is about 9554.1467436920. The cubic root of 91281720 is about 450.2578275581.

Adding to 91281720 its reverse (2718219), we get a palindrome (93999939).

The spelling of 91281720 in words is "ninety-one million, two hundred eighty-one thousand, seven hundred twenty".