21921169 has 2 divisors, whose sum is σ = 21921170. Its totient is φ = 21921168.

The previous prime is 21921167. The next prime is 21921191. The reversal of 21921169 is 96112912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21902400 + 18769 = 4680^2 + 137^2 .

It is a cyclic number.

It is not a de Polignac number, because 21921169 - 2¹ = 21921167 is a prime.

It is a super-2 number, since 2×21921169² = 961075300653122, which contains 22 as substring.

Together with 21921167, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21921169.

It is not a weakly prime, because it can be changed into another prime (21921167) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10960584 + 10960585.

It is an arithmetic number, because the mean of its divisors is an integer number (10960585).

Almost surely, 2^21921169 is an apocalyptic number.

It is an amenable number.

21921169 is a deficient number, since it is larger than the sum of its proper divisors (1).

21921169 is an equidigital number, since it uses as much as digits as its factorization.

21921169 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1944, while the sum is 31.

The square root of 21921169 is about 4682.0048056361. The cubic root of 21921169 is about 279.8688544003.

The spelling of 21921169 in words is "twenty-one million, nine hundred twenty-one thousand, one hundred sixty-nine".