21543569 has 2 divisors, whose sum is σ = 21543570. Its totient is φ = 21543568.

The previous prime is 21543551. The next prime is 21543589. The reversal of 21543569 is 96534512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16703569 + 4840000 = 4087^2 + 2200^2 .

It is a cyclic number.

It is not a de Polignac number, because 21543569 - 2²⁰ = 20494993 is a prime.

It is a super-2 number, since 2×21543569² = 928250730515522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21543589) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771784 + 10771785.

It is an arithmetic number, because the mean of its divisors is an integer number (10771785).

Almost surely, 2^21543569 is an apocalyptic number.

It is an amenable number.

21543569 is a deficient number, since it is larger than the sum of its proper divisors (1).

21543569 is an equidigital number, since it uses as much as digits as its factorization.

21543569 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32400, while the sum is 35.

The square root of 21543569 is about 4641.5050360847. The cubic root of 21543569 is about 278.2525911908.

The spelling of 21543569 in words is "twenty-one million, five hundred forty-three thousand, five hundred sixty-nine".