21729269 has 2 divisors, whose sum is σ = 21729270. Its totient is φ = 21729268.

The previous prime is 21729263. The next prime is 21729289. The reversal of 21729269 is 96292712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20584369 + 1144900 = 4537^2 + 1070^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21729269 is a prime.

It is a super-2 number, since 2×21729269² = 944322262548722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21729263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10864634 + 10864635.

It is an arithmetic number, because the mean of its divisors is an integer number (10864635).

Almost surely, 2^21729269 is an apocalyptic number.

It is an amenable number.

21729269 is a deficient number, since it is larger than the sum of its proper divisors (1).

21729269 is an equidigital number, since it uses as much as digits as its factorization.

21729269 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 38.

The square root of 21729269 is about 4661.4664001792. The cubic root of 21729269 is about 279.0497934877.

It can be divided in two parts, 2 and 1729269, that added together give a palindrome (1729271).

The spelling of 21729269 in words is "twenty-one million, seven hundred twenty-nine thousand, two hundred sixty-nine".