91533781 has 4 divisors (see below), whose sum is σ = 92063052. Its totient is φ = 91004512.

The previous prime is 91533749. The next prime is 91533787. The reversal of 91533781 is 18733519.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18733519 = 7 ⋅2676217.

It can be written as a sum of positive squares in 2 ways, for example, as 39564100 + 51969681 = 6290^2 + 7209^2 .

It is a cyclic number.

It is not a de Polignac number, because 91533781 - 2⁵ = 91533749 is a prime.

It is a super-2 number, since 2×91533781² = 16756866128311922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 91533781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91533787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264376 + ... + 264721.

It is an arithmetic number, because the mean of its divisors is an integer number (23015763).

Almost surely, 2^91533781 is an apocalyptic number.

It is an amenable number.

91533781 is a deficient number, since it is larger than the sum of its proper divisors (529271).

91533781 is a wasteful number, since it uses less digits than its factorization.

91533781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 529270.

The product of its digits is 22680, while the sum is 37.

The square root of 91533781 is about 9567.3288330652. The cubic root of 91533781 is about 450.6718868536.

The spelling of 91533781 in words is "ninety-one million, five hundred thirty-three thousand, seven hundred eighty-one".