91371781 has 4 divisors (see below), whose sum is σ = 91736064. Its totient is φ = 91007500.

The previous prime is 91371767. The next prime is 91371799. The reversal of 91371781 is 18717319.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 91371781 - 2⁷ = 91371653 is a prime.

It is a super-2 number, since 2×91371781² = 16697604726223922, 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 91371781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91371701) 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, 181765 + ... + 182266.

It is an arithmetic number, because the mean of its divisors is an integer number (22934016).

Almost surely, 2^91371781 is an apocalyptic number.

It is an amenable number.

91371781 is a deficient number, since it is larger than the sum of its proper divisors (364283).

91371781 is a wasteful number, since it uses less digits than its factorization.

91371781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364282.

The product of its digits is 10584, while the sum is 37.

The square root of 91371781 is about 9558.8587707948. The cubic root of 91371781 is about 450.4058577127.

The spelling of 91371781 in words is "ninety-one million, three hundred seventy-one thousand, seven hundred eighty-one".