21728206 has 8 divisors (see below), whose sum is σ = 32714280. Its totient is φ = 10823448.

The previous prime is 21728197. The next prime is 21728233. The reversal of 21728206 is 60282712.

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

It is a super-2 number, since 2×21728206² = 944229871956872, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19656 + ... + 20731.

It is an arithmetic number, because the mean of its divisors is an integer number (4089285).

Almost surely, 2^21728206 is an apocalyptic number.

21728206 is a deficient number, since it is larger than the sum of its proper divisors (10986074).

21728206 is a wasteful number, since it uses less digits than its factorization.

21728206 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40658.

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 21728206 is about 4661.3523788703. The cubic root of 21728206 is about 279.0452430237.

The spelling of 21728206 in words is "twenty-one million, seven hundred twenty-eight thousand, two hundred six".