1161306721 has 4 divisors (see below), whose sum is σ = 1161379012. Its totient is φ = 1161234432.

The previous prime is 1161306697. The next prime is 1161306739. The reversal of 1161306721 is 1276031611.

1161306721 is a nontrivial binomial coefficient, being equal to C(48194, 2).

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 897601600 + 263705121 = 29960^2 + 16239^2 .

It is a 3-Lehmer number, since φ(1161306721) divides (1161306721-1)³.

It is a cyclic number.

It is not a de Polignac number, because 1161306721 - 2⁵ = 1161306689 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1161306721.

It is not an unprimeable number, because it can be changed into a prime (1161306761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1 + ... + 48193.

It is an arithmetic number, because the mean of its divisors is an integer number (290344753).

It is a Poulet number, since it divides 2^1161306720-1.

Almost surely, 2^1161306721 is an apocalyptic number.

1161306721 is the 48193-rd triangular number and also the 24097-th hexagonal number.

1161306721 is the 16065-th centered nonagonal number.

It is an amenable number.

1161306721 is a deficient number, since it is larger than the sum of its proper divisors (72291).

1161306721 is an equidigital number, since it uses as much as digits as its factorization.

1161306721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72290.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 1161306721 is about 34077.9506572798. The cubic root of 1161306721 is about 1051.1119651566. Note that the first 3 decimals are identical.

The spelling of 1161306721 in words is "one billion, one hundred sixty-one million, three hundred six thousand, seven hundred twenty-one".