11867705721 has 9 divisors (see below), whose sum is σ = 17142713679. Its totient is φ = 7911585936.

The previous prime is 11867705687. The next prime is 11867705723. The reversal of 11867705721 is 12750776811.

The square root of 11867705721 is 108939.

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

11867705721 is a `hidden beast` number, since 1 + 1 + 8 + 6 + 7 + 70 + 572 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1517492025 + 10350213696 = 38955^2 + 101736^2 .

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

It is not a de Polignac number, because 11867705721 - 2¹⁹ = 11867181433 is a prime.

It is a super-2 number, since 2×11867705721² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (11867705723) 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 8 ways as a sum of consecutive naturals, for example, 308661 + ... + 344973.

Almost surely, 2^11867705721 is an apocalyptic number.

11867705721 is the 108939-th square number.

11867705721 is the 54470-th centered octagonal number.

It is an amenable number.

11867705721 is a deficient number, since it is larger than the sum of its proper divisors (5275007958).

11867705721 is an frugal number, since it uses more digits than its factorization.

11867705721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72632 (or 36316 counting only the distinct ones).

The product of its (nonzero) digits is 164640, while the sum is 45.

The spelling of 11867705721 in words is "eleven billion, eight hundred sixty-seven million, seven hundred five thousand, seven hundred twenty-one".