91861399781 has 2 divisors, whose sum is σ = 91861399782. Its totient is φ = 91861399780.

The previous prime is 91861399753. The next prime is 91861399811. The reversal of 91861399781 is 18799316819.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76920249025 + 14941150756 = 277345^2 + 122234^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91861399781 is a prime.

It is a super-2 number, since 2×91861399781² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91861359781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45930699890 + 45930699891.

It is an arithmetic number, because the mean of its divisors is an integer number (45930699891).

Almost surely, 2^91861399781 is an apocalyptic number.

It is an amenable number.

91861399781 is a deficient number, since it is larger than the sum of its proper divisors (1).

91861399781 is an equidigital number, since it uses as much as digits as its factorization.

91861399781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5878656, while the sum is 62.

The spelling of 91861399781 in words is "ninety-one billion, eight hundred sixty-one million, three hundred ninety-nine thousand, seven hundred eighty-one".