91780138581 has 4 divisors (see below), whose sum is σ = 122373518112. Its totient is φ = 61186759052.

The previous prime is 91780138579. The next prime is 91780138589. The reversal of 91780138581 is 18583108719.

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 91780138581 - 2¹ = 91780138579 is a prime.

It is a super-2 number, since 2×91780138581² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91780138589) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15296689761 + ... + 15296689766.

It is an arithmetic number, because the mean of its divisors is an integer number (30593379528).

Almost surely, 2^91780138581 is an apocalyptic number.

It is an amenable number.

91780138581 is a deficient number, since it is larger than the sum of its proper divisors (30593379531).

91780138581 is a wasteful number, since it uses less digits than its factorization.

91780138581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30593379530.

The product of its (nonzero) digits is 483840, while the sum is 51.

The spelling of 91780138581 in words is "ninety-one billion, seven hundred eighty million, one hundred thirty-eight thousand, five hundred eighty-one".