21081161 has 2 divisors, whose sum is σ = 21081162. Its totient is φ = 21081160.

The previous prime is 21081143. The next prime is 21081169. The reversal of 21081161 is 16118012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11095561 + 9985600 = 3331^2 + 3160^2 .

It is a cyclic number.

It is not a de Polignac number, because 21081161 - 2¹⁸ = 20819017 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21081169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10540580 + 10540581.

It is an arithmetic number, because the mean of its divisors is an integer number (10540581).

Almost surely, 2^21081161 is an apocalyptic number.

It is an amenable number.

21081161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21081161 is an equidigital number, since it uses as much as digits as its factorization.

21081161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 20.

The square root of 21081161 is about 4591.4225464446. The cubic root of 21081161 is about 276.2473846179.

Adding to 21081161 its reverse (16118012), we get a palindrome (37199173).

The spelling of 21081161 in words is "twenty-one million, eighty-one thousand, one hundred sixty-one".