21729359 has 4 divisors (see below), whose sum is σ = 22085640. Its totient is φ = 21373080.

The previous prime is 21729341. The next prime is 21729361. The reversal of 21729359 is 95392712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21729359 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 (21729329) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 178049 + ... + 178170.

It is an arithmetic number, because the mean of its divisors is an integer number (5521410).

Almost surely, 2^21729359 is an apocalyptic number.

21729359 is a deficient number, since it is larger than the sum of its proper divisors (356281).

21729359 is an equidigital number, since it uses as much as digits as its factorization.

21729359 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 356280.

The product of its digits is 34020, while the sum is 38.

The square root of 21729359 is about 4661.4760537838. The cubic root of 21729359 is about 279.0501787506.

The spelling of 21729359 in words is "twenty-one million, seven hundred twenty-nine thousand, three hundred fifty-nine".