21523153 has 4 divisors (see below), whose sum is σ = 21826368. Its totient is φ = 21219940.

The previous prime is 21523093. The next prime is 21523171. The reversal of 21523153 is 35132512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21523153 is a prime.

It is a super-3 number, since 3×21523153³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21523753) 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 3 ways as a sum of consecutive naturals, for example, 151501 + ... + 151642.

It is an arithmetic number, because the mean of its divisors is an integer number (5456592).

Almost surely, 2^21523153 is an apocalyptic number.

It is an amenable number.

21523153 is a deficient number, since it is larger than the sum of its proper divisors (303215).

21523153 is an equidigital number, since it uses as much as digits as its factorization.

21523153 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 303214.

The product of its digits is 900, while the sum is 22.

The square root of 21523153 is about 4639.3052281565. The cubic root of 21523153 is about 278.1646670351.

Adding to 21523153 its reverse (35132512), we get a palindrome (56655665).

The spelling of 21523153 in words is "twenty-one million, five hundred twenty-three thousand, one hundred fifty-three".