21549161 has 2 divisors, whose sum is σ = 21549162. Its totient is φ = 21549160.

The previous prime is 21549131. The next prime is 21549163. The reversal of 21549161 is 16194512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11689561 + 9859600 = 3419^2 + 3140^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21549161 is a prime.

It is a Sophie Germain prime.

Together with 21549163, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21549163) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10774580 + 10774581.

It is an arithmetic number, because the mean of its divisors is an integer number (10774581).

Almost surely, 2^21549161 is an apocalyptic number.

It is an amenable number.

21549161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21549161 is an equidigital number, since it uses as much as digits as its factorization.

21549161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 29.

The square root of 21549161 is about 4642.1073878143. The cubic root of 21549161 is about 278.2766641733.

The spelling of 21549161 in words is "twenty-one million, five hundred forty-nine thousand, one hundred sixty-one".