21208385 has 8 divisors (see below), whose sum is σ = 27763776. Its totient is φ = 15424240.

The previous prime is 21208373. The next prime is 21208387. The reversal of 21208385 is 58380212.

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

It is not a de Polignac number, because 21208385 - 2²⁰ = 20159809 is a prime.

It is a super-3 number, since 3×21208385³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21208387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 192749 + ... + 192858.

It is an arithmetic number, because the mean of its divisors is an integer number (3470472).

Almost surely, 2^21208385 is an apocalyptic number.

It is an amenable number.

21208385 is a deficient number, since it is larger than the sum of its proper divisors (6555391).

21208385 is a wasteful number, since it uses less digits than its factorization.

21208385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 385623.

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 21208385 is about 4605.2562360850. The cubic root of 21208385 is about 276.8019845785.

Adding to 21208385 its reverse (58380212), we get a palindrome (79588597).

The spelling of 21208385 in words is "twenty-one million, two hundred eight thousand, three hundred eighty-five".