21719729 has 8 divisors (see below), whose sum is σ = 22161120. Its totient is φ = 21280896.

The previous prime is 21719699. The next prime is 21719741. The reversal of 21719729 is 92791712.

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 21719729 - 2²⁴ = 4942513 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21719692 and 21719701.

It is not an unprimeable number, because it can be changed into a prime (21719749) 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, 31937 + ... + 32609.

It is an arithmetic number, because the mean of its divisors is an integer number (2770140).

Almost surely, 2^21719729 is an apocalyptic number.

It is an amenable number.

21719729 is a deficient number, since it is larger than the sum of its proper divisors (441391).

21719729 is an equidigital number, since it uses as much as digits as its factorization.

21719729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1279.

The product of its digits is 15876, while the sum is 38.

The square root of 21719729 is about 4660.4430046939. The cubic root of 21719729 is about 279.0089495808.

The spelling of 21719729 in words is "twenty-one million, seven hundred nineteen thousand, seven hundred twenty-nine".