21729079 has 2 divisors, whose sum is σ = 21729080. Its totient is φ = 21729078.

The previous prime is 21729031. The next prime is 21729119. The reversal of 21729079 is 97092712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21729079 - 2¹⁹ = 21204791 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21799079) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10864539 + 10864540.

It is an arithmetic number, because the mean of its divisors is an integer number (10864540).

Almost surely, 2^21729079 is an apocalyptic number.

21729079 is a deficient number, since it is larger than the sum of its proper divisors (1).

21729079 is an equidigital number, since it uses as much as digits as its factorization.

21729079 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15876, while the sum is 37.

The square root of 21729079 is about 4661.4460202817. The cubic root of 21729079 is about 279.0489801513.

The spelling of 21729079 in words is "twenty-one million, seven hundred twenty-nine thousand, seventy-nine".