21155161 has 2 divisors, whose sum is σ = 21155162. Its totient is φ = 21155160.

The previous prime is 21155159. The next prime is 21155171. The reversal of 21155161 is 16155112.

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., 11943936 + 9211225 = 3456^2 + 3035^2 .

It is a cyclic number.

It is not a de Polignac number, because 21155161 - 2¹ = 21155159 is a prime.

Together with 21155159, 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 (21155131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577580 + 10577581.

It is an arithmetic number, because the mean of its divisors is an integer number (10577581).

Almost surely, 2^21155161 is an apocalyptic number.

It is an amenable number.

21155161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21155161 is an equidigital number, since it uses as much as digits as its factorization.

21155161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 300, while the sum is 22.

The square root of 21155161 is about 4599.4739916647. The cubic root of 21155161 is about 276.5702389718.

It can be divided in two parts, 21155 and 161, that added together give a square (21316 = 146²).

The spelling of 21155161 in words is "twenty-one million, one hundred fifty-five thousand, one hundred sixty-one".