21251255 has 4 divisors (see below), whose sum is σ = 25501512. Its totient is φ = 17001000.

The previous prime is 21251239. The next prime is 21251257. The reversal of 21251255 is 55215212.

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

It is not a de Polignac number, because 21251255 - 2⁴ = 21251239 is a prime.

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 21251255.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251257) 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, 2125121 + ... + 2125130.

It is an arithmetic number, because the mean of its divisors is an integer number (6375378).

Almost surely, 2^21251255 is an apocalyptic number.

21251255 is a deficient number, since it is larger than the sum of its proper divisors (4250257).

21251255 is an equidigital number, since it uses as much as digits as its factorization.

21251255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4250256.

The product of its digits is 1000, while the sum is 23.

The square root of 21251255 is about 4609.9083504990. The cubic root of 21251255 is about 276.9883654920.

Adding to 21251255 its reverse (55215212), we get a palindrome (76466467).

The spelling of 21251255 in words is "twenty-one million, two hundred fifty-one thousand, two hundred fifty-five".