21330523 has 4 divisors (see below), whose sum is σ = 21484120. Its totient is φ = 21176928.

The previous prime is 21330503. The next prime is 21330581. The reversal of 21330523 is 32503312.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21330523 - 2¹³ = 21322331 is a prime.

It is a super-2 number, since 2×21330523² = 909982422907058, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21330523.

It is not an unprimeable number, because it can be changed into a prime (21330503) 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, 76590 + ... + 76867.

It is an arithmetic number, because the mean of its divisors is an integer number (5371030).

Almost surely, 2^21330523 is an apocalyptic number.

21330523 is a deficient number, since it is larger than the sum of its proper divisors (153597).

21330523 is a wasteful number, since it uses less digits than its factorization.

21330523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153596.

The product of its (nonzero) digits is 540, while the sum is 19.

The square root of 21330523 is about 4618.4979159896. The cubic root of 21330523 is about 277.3323306036.

Adding to 21330523 its reverse (32503312), we get a palindrome (53833835).

The spelling of 21330523 in words is "twenty-one million, three hundred thirty thousand, five hundred twenty-three".