21643461161 has 6 divisors (see below), whose sum is σ = 25177087530. Its totient is φ = 18551538096.

The previous prime is 21643461143. The next prime is 21643461187. The reversal of 21643461161 is 16116434612.

It can be written as a sum of positive squares in only one way, i.e., 13018810000 + 8624651161 = 114100^2 + 92869^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21643461161 is a prime.

It is a super-2 number, since 2×21643461161² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21643461101) 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 5 ways as a sum of consecutive naturals, for example, 220851596 + ... + 220851693.

It is an arithmetic number, because the mean of its divisors is an integer number (4196181255).

Almost surely, 2^21643461161 is an apocalyptic number.

It is an amenable number.

21643461161 is a deficient number, since it is larger than the sum of its proper divisors (3533626369).

21643461161 is an equidigital number, since it uses as much as digits as its factorization.

21643461161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 441703303 (or 441703296 counting only the distinct ones).

The product of its digits is 20736, while the sum is 35.

Adding to 21643461161 its reverse (16116434612), we get a palindrome (37759895773).

The spelling of 21643461161 in words is "twenty-one billion, six hundred forty-three million, four hundred sixty-one thousand, one hundred sixty-one".