91694501721 has 9 divisors (see below), whose sum is σ = 132448925791. Its totient is φ = 61129062192.

The previous prime is 91694501687. The next prime is 91694501729. The reversal of 91694501721 is 12710549619.

The square root of 91694501721 is 302811.

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

91694501721 is a `hidden beast` number, since 9 + 169 + 450 + 17 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 9935105625 + 81759396096 = 99675^2 + 285936^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 91694501721 - 2²⁵ = 91660947289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91694501729) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 857965 + ... + 958901.

Almost surely, 2^91694501721 is an apocalyptic number.

91694501721 is the 302811-st square number.

91694501721 is the 151406-th centered octagonal number.

It is an amenable number.

91694501721 is a deficient number, since it is larger than the sum of its proper divisors (40754424070).

91694501721 is an frugal number, since it uses more digits than its factorization.

91694501721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 201880 (or 100940 counting only the distinct ones).

The product of its (nonzero) digits is 136080, while the sum is 45.

The spelling of 91694501721 in words is "ninety-one billion, six hundred ninety-four million, five hundred one thousand, seven hundred twenty-one".