21645353 has 4 divisors (see below), whose sum is σ = 21657348. Its totient is φ = 21633360.

The previous prime is 21645343. The next prime is 21645373. The reversal of 21645353 is 35354612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 17205904 + 4439449 = 4148^2 + 2107^2 .

It is a cyclic number.

It is not a de Polignac number, because 21645353 - 2¹⁴ = 21628969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21645343) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2678 + ... + 7103.

It is an arithmetic number, because the mean of its divisors is an integer number (5414337).

Almost surely, 2^21645353 is an apocalyptic number.

It is an amenable number.

21645353 is a deficient number, since it is larger than the sum of its proper divisors (11995).

21645353 is an equidigital number, since it uses as much as digits as its factorization.

21645353 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11994.

The product of its digits is 10800, while the sum is 29.

The square root of 21645353 is about 4652.4566628825. The cubic root of 21645353 is about 278.6901104017.

Adding to 21645353 its reverse (35354612), we get a palindrome (56999965).

The spelling of 21645353 in words is "twenty-one million, six hundred forty-five thousand, three hundred fifty-three".