21865241161 has 9 divisors (see below), whose sum is σ = 22206520749. Its totient is φ = 21529134924.

The previous prime is 21865241149. The next prime is 21865241171. The reversal of 21865241161 is 16114256812.

The square root of 21865241161 is 147869.

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

It is not a de Polignac number, because 21865241161 - 2¹¹ = 21865239113 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21865241161.

It is not an unprimeable number, because it can be changed into a prime (21865241171) 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, 9906120 + ... + 9908326.

Almost surely, 2^21865241161 is an apocalyptic number.

21865241161 is the 147869-th square number.

21865241161 is the 73935-th centered octagonal number.

It is an amenable number.

21865241161 is a deficient number, since it is larger than the sum of its proper divisors (341279588).

21865241161 is an frugal number, since it uses more digits than its factorization.

21865241161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4548 (or 2274 counting only the distinct ones).

The product of its digits is 23040, while the sum is 37.

Adding to 21865241161 its reverse (16114256812), we get a palindrome (37979497973).

The spelling of 21865241161 in words is "twenty-one billion, eight hundred sixty-five million, two hundred forty-one thousand, one hundred sixty-one".