21729511 has 2 divisors, whose sum is σ = 21729512. Its totient is φ = 21729510.

The previous prime is 21729509. The next prime is 21729517. The reversal of 21729511 is 11592712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21729511 - 2¹ = 21729509 is a prime.

Together with 21729509, 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 21729511.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21729517) 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, 10864755 + 10864756.

It is an arithmetic number, because the mean of its divisors is an integer number (10864756).

Almost surely, 2^21729511 is an apocalyptic number.

21729511 is a deficient number, since it is larger than the sum of its proper divisors (1).

21729511 is an equidigital number, since it uses as much as digits as its factorization.

21729511 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1260, while the sum is 28.

The square root of 21729511 is about 4661.4923576039. The cubic root of 21729511 is about 279.0508294145.

The spelling of 21729511 in words is "twenty-one million, seven hundred twenty-nine thousand, five hundred eleven".