21716205 has 16 divisors (see below), whose sum is σ = 39709824. Its totient is φ = 9927360.

The previous prime is 21716159. The next prime is 21716237. The reversal of 21716205 is 50261712.

It is not a de Polignac number, because 21716205 - 2¹¹ = 21714157 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 103306 + ... + 103515.

It is an arithmetic number, because the mean of its divisors is an integer number (2481864).

Almost surely, 2^21716205 is an apocalyptic number.

It is an amenable number.

21716205 is a deficient number, since it is larger than the sum of its proper divisors (17993619).

21716205 is a wasteful number, since it uses less digits than its factorization.

21716205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206836.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21716205 is about 4660.0649137110. The cubic root of 21716205 is about 278.9938591421.

Adding to 21716205 its reverse (50261712), we get a palindrome (71977917).

The spelling of 21716205 in words is "twenty-one million, seven hundred sixteen thousand, two hundred five".