21308645 has 8 divisors (see below), whose sum is σ = 25673760. Its totient is φ = 16978000.

The previous prime is 21308629. The next prime is 21308653. The reversal of 21308645 is 54680312.

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

It is not a de Polignac number, because 21308645 - 2⁴ = 21308629 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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, 7235 + ... + 9744.

It is an arithmetic number, because the mean of its divisors is an integer number (3209220).

Almost surely, 2^21308645 is an apocalyptic number.

It is an amenable number.

21308645 is a deficient number, since it is larger than the sum of its proper divisors (4365115).

21308645 is a wasteful number, since it uses less digits than its factorization.

21308645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17235.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21308645 is about 4616.1287893645. The cubic root of 21308645 is about 277.2374813537.

Adding to 21308645 its reverse (54680312), we get a palindrome (75988957).

The spelling of 21308645 in words is "twenty-one million, three hundred eight thousand, six hundred forty-five".