21255523 has 4 divisors (see below), whose sum is σ = 21266280. Its totient is φ = 21244768.

The previous prime is 21255497. The next prime is 21255529. The reversal of 21255523 is 32555212.

It is a happy number.

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 is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21255523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21255529) 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, 1465 + ... + 6682.

It is an arithmetic number, because the mean of its divisors is an integer number (5316570).

Almost surely, 2^21255523 is an apocalyptic number.

21255523 is a deficient number, since it is larger than the sum of its proper divisors (10757).

21255523 is an equidigital number, since it uses as much as digits as its factorization.

21255523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10756.

The product of its digits is 3000, while the sum is 25.

The square root of 21255523 is about 4610.3712431864. The cubic root of 21255523 is about 277.0069072552.

The spelling of 21255523 in words is "twenty-one million, two hundred fifty-five thousand, five hundred twenty-three".