21135161 has 2 divisors, whose sum is σ = 21135162. Its totient is φ = 21135160.

The previous prime is 21135151. The next prime is 21135173. The reversal of 21135161 is 16153112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20839225 + 295936 = 4565^2 + 544^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21135161 is a prime.

It is not a weakly prime, because it can be changed into another prime (21135151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10567580 + 10567581.

It is an arithmetic number, because the mean of its divisors is an integer number (10567581).

Almost surely, 2^21135161 is an apocalyptic number.

It is an amenable number.

21135161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135161 is an equidigital number, since it uses as much as digits as its factorization.

21135161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 180, while the sum is 20.

The square root of 21135161 is about 4597.2993159028. The cubic root of 21135161 is about 276.4830553792.

Adding to 21135161 its reverse (16153112), we get a palindrome (37288273).

The spelling of 21135161 in words is "twenty-one million, one hundred thirty-five thousand, one hundred sixty-one".