21829729 has 2 divisors, whose sum is σ = 21829730. Its totient is φ = 21829728.

The previous prime is 21829723. The next prime is 21829763. The reversal of 21829729 is 92792812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17305600 + 4524129 = 4160^2 + 2127^2 .

It is a cyclic number.

It is not a de Polignac number, because 21829729 - 2⁹ = 21829217 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21829691 and 21829700.

It is not a weakly prime, because it can be changed into another prime (21829723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10914864 + 10914865.

It is an arithmetic number, because the mean of its divisors is an integer number (10914865).

Almost surely, 2^21829729 is an apocalyptic number.

It is an amenable number.

21829729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21829729 is an equidigital number, since it uses as much as digits as its factorization.

21829729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 40.

The square root of 21829729 is about 4672.2295534359. The cubic root of 21829729 is about 279.4791721151.

It can be divided in two parts, 2182 and 9729, that added together give a palindrome (11911).

The spelling of 21829729 in words is "twenty-one million, eight hundred twenty-nine thousand, seven hundred twenty-nine".