21423161 has 2 divisors, whose sum is σ = 21423162. Its totient is φ = 21423160.

The previous prime is 21423119. The next prime is 21423163. The reversal of 21423161 is 16132412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21114025 + 309136 = 4595^2 + 556^2 .

It is a cyclic number.

It is not a de Polignac number, because 21423161 - 2¹⁸ = 21161017 is a prime.

Together with 21423163, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21423163) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10711580 + 10711581.

It is an arithmetic number, because the mean of its divisors is an integer number (10711581).

Almost surely, 2^21423161 is an apocalyptic number.

It is an amenable number.

21423161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21423161 is an equidigital number, since it uses as much as digits as its factorization.

21423161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 20.

The square root of 21423161 is about 4628.5160688929. The cubic root of 21423161 is about 277.7332335625.

Adding to 21423161 its reverse (16132412), we get a palindrome (37555573).

The spelling of 21423161 in words is "twenty-one million, four hundred twenty-three thousand, one hundred sixty-one".