21161013141581 has 2 divisors, whose sum is σ = 21161013141582. Its totient is φ = 21161013141580.

The previous prime is 21161013141571. The next prime is 21161013141601. The reversal of 21161013141581 is 18514131016112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16904095108681 + 4256918032900 = 4111459^2 + 2063230^2 .

It is a cyclic number.

It is not a de Polignac number, because 21161013141581 - 2¹⁰ = 21161013140557 is a prime.

It is a super-2 number, since 2×21161013141581² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21161013141571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10580506570790 + 10580506570791.

It is an arithmetic number, because the mean of its divisors is an integer number (10580506570791).

Almost surely, 2^{21161013141581} is an apocalyptic number.

It is an amenable number.

21161013141581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21161013141581 is an equidigital number, since it uses as much as digits as its factorization.

21161013141581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5760, while the sum is 35.

Adding to 21161013141581 its reverse (18514131016112), we get a palindrome (39675144157693).

The spelling of 21161013141581 in words is "twenty-one trillion, one hundred sixty-one billion, thirteen million, one hundred forty-one thousand, five hundred eighty-one".