21729238 has 4 divisors (see below), whose sum is σ = 32593860. Its totient is φ = 10864618.

The previous prime is 21729229. The next prime is 21729263. The reversal of 21729238 is 83292712.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5432308 + ... + 5432311.

It is an arithmetic number, because the mean of its divisors is an integer number (8148465).

Almost surely, 2^21729238 is an apocalyptic number.

21729238 is a deficient number, since it is larger than the sum of its proper divisors (10864622).

21729238 is a wasteful number, since it uses less digits than its factorization.

21729238 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10864621.

The product of its digits is 12096, while the sum is 34.

The square root of 21729238 is about 4661.4630750441. The cubic root of 21729238 is about 279.0496607858.

The spelling of 21729238 in words is "twenty-one million, seven hundred twenty-nine thousand, two hundred thirty-eight".