21108169 has 12 divisors (see below), whose sum is σ = 22757436. Its totient is φ = 19510272.

The previous prime is 21108163. The next prime is 21108173. The reversal of 21108169 is 96180112.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 67600 + 21040569 = 260^2 + 4587^2 .

It is not a de Polignac number, because 21108169 - 2⁵ = 21108137 is a prime.

It is a super-2 number, since 2×21108169² = 891109597065122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21108163) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 90477 + ... + 90709.

It is an arithmetic number, because the mean of its divisors is an integer number (1896453).

Almost surely, 2^21108169 is an apocalyptic number.

It is an amenable number.

21108169 is a deficient number, since it is larger than the sum of its proper divisors (1649267).

21108169 is an equidigital number, since it uses as much as digits as its factorization.

21108169 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396 (or 323 counting only the distinct ones).

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

The square root of 21108169 is about 4594.3627414474. The cubic root of 21108169 is about 276.3653051548.

The spelling of 21108169 in words is "twenty-one million, one hundred eight thousand, one hundred sixty-nine".