21844729 has 2 divisors, whose sum is σ = 21844730. Its totient is φ = 21844728.

The previous prime is 21844727. The next prime is 21844751. The reversal of 21844729 is 92744812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21409129 + 435600 = 4627^2 + 660^2 .

It is a cyclic number.

It is not a de Polignac number, because 21844729 - 2¹ = 21844727 is a prime.

Together with 21844727, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21844727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10922364 + 10922365.

It is an arithmetic number, because the mean of its divisors is an integer number (10922365).

Almost surely, 2^21844729 is an apocalyptic number.

It is an amenable number.

21844729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21844729 is an equidigital number, since it uses as much as digits as its factorization.

21844729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32256, while the sum is 37.

The square root of 21844729 is about 4673.8345071258. The cubic root of 21844729 is about 279.5431708901.

The spelling of 21844729 in words is "twenty-one million, eight hundred forty-four thousand, seven hundred twenty-nine".