21729307 has 2 divisors, whose sum is σ = 21729308. Its totient is φ = 21729306.

The previous prime is 21729289. The next prime is 21729313. The reversal of 21729307 is 70392712.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21729307 is a prime.

It is not a weakly prime, because it can be changed into another prime (21729377) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10864653 + 10864654.

It is an arithmetic number, because the mean of its divisors is an integer number (10864654).

Almost surely, 2^21729307 is an apocalyptic number.

21729307 is a deficient number, since it is larger than the sum of its proper divisors (1).

21729307 is an equidigital number, since it uses as much as digits as its factorization.

21729307 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5292, while the sum is 31.

The square root of 21729307 is about 4661.4704761481. The cubic root of 21729307 is about 279.0499561544.

The spelling of 21729307 in words is "twenty-one million, seven hundred twenty-nine thousand, three hundred seven".