91778639872 has 24 divisors (see below), whose sum is σ = 183512470050. Its totient is φ = 45889318912.

The previous prime is 91778639863. The next prime is 91778639873. The reversal of 91778639872 is 27893687719.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 88508630016 + 3270009856 = 297504^2 + 57184^2 .

It is a junction number, because it is equal to n+sod(n) for n = 91778639798 and 91778639807.

It is not an unprimeable number, because it can be changed into a prime (91778639873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 22404847 + ... + 22408942.

Almost surely, 2^91778639872 is an apocalyptic number.

It is an amenable number.

91778639872 is a deficient number, since it is larger than the sum of its proper divisors (91733830178).

91778639872 is an equidigital number, since it uses as much as digits as its factorization.

91778639872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44813811 (or 44813791 counting only the distinct ones).

The product of its digits is 64012032, while the sum is 67.

The spelling of 91778639872 in words is "ninety-one billion, seven hundred seventy-eight million, six hundred thirty-nine thousand, eight hundred seventy-two".