21506730621161 has 2 divisors, whose sum is σ = 21506730621162. Its totient is φ = 21506730621160.

The previous prime is 21506730621043. The next prime is 21506730621169. The reversal of 21506730621161 is 16112603760512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21471778075225 + 34952545936 = 4633765^2 + 186956^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506730621161 - 2¹⁸ = 21506730359017 is a prime.

It is a super-3 number, since 3×21506730621161³ (a number of 41 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (21506730621169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753365310580 + 10753365310581.

It is an arithmetic number, because the mean of its divisors is an integer number (10753365310581).

Almost surely, 2^{21506730621161} is an apocalyptic number.

It is an amenable number.

21506730621161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506730621161 is an equidigital number, since it uses as much as digits as its factorization.

21506730621161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 90720, while the sum is 41.

The spelling of 21506730621161 in words is "twenty-one trillion, five hundred six billion, seven hundred thirty million, six hundred twenty-one thousand, one hundred sixty-one".