21729847 has 8 divisors (see below), whose sum is σ = 22311072. Its totient is φ = 21156000.

The previous prime is 21729821. The next prime is 21729889. The reversal of 21729847 is 74892712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21729847 - 2¹¹ = 21727799 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21729647) 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 in 7 ways as a sum of consecutive naturals, for example, 4398 + ... + 7924.

It is an arithmetic number, because the mean of its divisors is an integer number (2788884).

Almost surely, 2^21729847 is an apocalyptic number.

21729847 is a deficient number, since it is larger than the sum of its proper divisors (581225).

21729847 is a wasteful number, since it uses less digits than its factorization.

21729847 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3689.

The product of its digits is 56448, while the sum is 40.

The square root of 21729847 is about 4661.5283974250. The cubic root of 21729847 is about 279.0522677134.

The spelling of 21729847 in words is "twenty-one million, seven hundred twenty-nine thousand, eight hundred forty-seven".