21321205 has 8 divisors (see below), whose sum is σ = 25615800. Its totient is φ = 17036736.

The previous prime is 21321203. The next prime is 21321217. The reversal of 21321205 is 50212312.

It can be written as a sum of positive squares in 4 ways, for example, as 1758276 + 19562929 = 1326^2 + 4423^2 .

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 21321205 - 2¹ = 21321203 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321203) 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, 3351 + ... + 7339.

It is an arithmetic number, because the mean of its divisors is an integer number (3201975).

Almost surely, 2^21321205 is an apocalyptic number.

It is an amenable number.

21321205 is a deficient number, since it is larger than the sum of its proper divisors (4294595).

21321205 is a wasteful number, since it uses less digits than its factorization.

21321205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5063.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21321205 is about 4617.4890362620. The cubic root of 21321205 is about 277.2919415480.

Adding to 21321205 its reverse (50212312), we get a palindrome (71533517).

The spelling of 21321205 in words is "twenty-one million, three hundred twenty-one thousand, two hundred five".