21368569 has 2 divisors, whose sum is σ = 21368570.
Its totient is φ = 21368568.
The previous prime is 21368539. The next prime is 21368591. The reversal of 21368569 is 96586312.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 20820969 + 547600 = 4563^2 + 740^2
It is a cyclic number.
It is not a de Polignac number, because 21368569 - 213 = 21360377 is a prime.
It is a super-2 number, since 2×213685692 = 913231482215522, which contains 22 as substring.
It is not a weakly prime, because it can be changed into another prime (21368539) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (13) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10684284 + 10684285.
It is an arithmetic number, because the mean of its divisors is an integer number (10684285).
Almost surely, 221368569 is an apocalyptic number.
It is an amenable number.
21368569 is a deficient number, since it is larger than the sum of its proper divisors (1).
21368569 is an equidigital number, since it uses as much as digits as its factorization.
21368569 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 77760, while the sum is 40.
The square root of 21368569 is about 4622.6149525999.
The cubic root of 21368569 is about 277.4971197926.
The spelling of 21368569 in words is "twenty-one million, three hundred sixty-eight thousand, five hundred sixty-nine".