91784811432721 has 27 divisors (see below), whose sum is σ = 102833147420017. Its totient is φ = 81861402296960.

The previous prime is 91784811432709. The next prime is 91784811432733. The reversal of 91784811432721 is 12723411848719.

The square root of 91784811432721 is 9580439.

It is a perfect power (a square), and thus also a powerful number.

It is an interprime number because it is at equal distance from previous prime (91784811432709) and next prime (91784811432733).

It can be written as a sum of positive squares in 4 ways, for example, as 56759483464321 + 35025327968400 = 7533889^2 + 5918220^2 .

It is not a de Polignac number, because 91784811432721 - 2¹¹ = 91784811430673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91784811432761) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 5585387721 + ... + 5585404153.

Almost surely, 2^{91784811432721} is an apocalyptic number.

91784811432721 is the 9580439-th square number.

91784811432721 is the 4790220-th centered octagonal number.

It is an amenable number.

91784811432721 is a deficient number, since it is larger than the sum of its proper divisors (11048335987296).

91784811432721 is an frugal number, since it uses more digits than its factorization.

91784811432721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32994 (or 16497 counting only the distinct ones).

The product of its digits is 5419008, while the sum is 58.

The spelling of 91784811432721 in words is "ninety-one trillion, seven hundred eighty-four billion, eight hundred eleven million, four hundred thirty-two thousand, seven hundred twenty-one".