20891161 has 2 divisors, whose sum is σ = 20891162. Its totient is φ = 20891160.

The previous prime is 20891149. The next prime is 20891197. The reversal of 20891161 is 16119802.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11861136 + 9030025 = 3444^2 + 3005^2 .

It is a cyclic number.

It is not a de Polignac number, because 20891161 - 2⁷ = 20891033 is a prime.

It is not a weakly prime, because it can be changed into another prime (20891131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10445580 + 10445581.

It is an arithmetic number, because the mean of its divisors is an integer number (10445581).

Almost surely, 2^20891161 is an apocalyptic number.

It is an amenable number.

20891161 is a deficient number, since it is larger than the sum of its proper divisors (1).

20891161 is an equidigital number, since it uses as much as digits as its factorization.

20891161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 20891161 is about 4570.6849596094. The cubic root of 20891161 is about 275.4149592104.

The spelling of 20891161 in words is "twenty million, eight hundred ninety-one thousand, one hundred sixty-one".