21729233 has 8 divisors (see below), whose sum is σ = 22953216. Its totient is φ = 20538000.

The previous prime is 21729229. The next prime is 21729263. The reversal of 21729233 is 33292712.

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 21729233 - 2² = 21729229 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21729196 and 21729205.

It is not an unprimeable number, because it can be changed into a prime (21729263) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6818 + ... + 9483.

It is an arithmetic number, because the mean of its divisors is an integer number (2869152).

Almost surely, 2^21729233 is an apocalyptic number.

It is an amenable number.

21729233 is a deficient number, since it is larger than the sum of its proper divisors (1223983).

21729233 is a wasteful number, since it uses less digits than its factorization.

21729233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16375.

The product of its digits is 4536, while the sum is 29.

The square root of 21729233 is about 4661.4625387318. The cubic root of 21729233 is about 279.0496393822.

The spelling of 21729233 in words is "twenty-one million, seven hundred twenty-nine thousand, two hundred thirty-three".