21240205 has 8 divisors (see below), whose sum is σ = 29129472. Its totient is φ = 14564688.

The previous prime is 21240179. The next prime is 21240211. The reversal of 21240205 is 50204212.

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 21240205 - 2⁹ = 21239693 is a prime.

It is a super-2 number, since 2×21240205² = 902292616884050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 303397 + ... + 303466.

It is an arithmetic number, because the mean of its divisors is an integer number (3641184).

Almost surely, 2^21240205 is an apocalyptic number.

It is an amenable number.

21240205 is a deficient number, since it is larger than the sum of its proper divisors (7889267).

21240205 is an equidigital number, since it uses as much as digits as its factorization.

21240205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 606875.

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21240205 is about 4608.7096892731. The cubic root of 21240205 is about 276.9403486873.

Adding to 21240205 its reverse (50204212), we get a palindrome (71444417).

The spelling of 21240205 in words is "twenty-one million, two hundred forty thousand, two hundred five".