21208345 has 8 divisors (see below), whose sum is σ = 25613064. Its totient is φ = 16857984.

The previous prime is 21208259. The next prime is 21208349. The reversal of 21208345 is 54380212.

It can be written as a sum of positive squares in 4 ways, for example, as 5621641 + 15586704 = 2371^2 + 3948^2 .

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 21208345 - 2¹⁵ = 21175577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21208349) 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, 12724 + ... + 14293.

It is an arithmetic number, because the mean of its divisors is an integer number (3201633).

Almost surely, 2^21208345 is an apocalyptic number.

It is an amenable number.

21208345 is a deficient number, since it is larger than the sum of its proper divisors (4404719).

21208345 is a wasteful number, since it uses less digits than its factorization.

21208345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27179.

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 21208345 is about 4605.2518932193. The cubic root of 21208345 is about 276.8018105579.

Adding to 21208345 its reverse (54380212), we get a palindrome (75588557).

The spelling of 21208345 in words is "twenty-one million, two hundred eight thousand, three hundred forty-five".