21240255 has 16 divisors (see below), whose sum is σ = 34814304. Its totient is φ = 11051520.

The previous prime is 21240253. The next prime is 21240283. The reversal of 21240255 is 55204212.

It is a happy number.

It is not a de Polignac number, because 21240255 - 2¹ = 21240253 is a prime.

It is a super-2 number, since 2×21240255² = 902296864930050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16654 + ... + 17883.

It is an arithmetic number, because the mean of its divisors is an integer number (2175894).

Almost surely, 2^21240255 is an apocalyptic number.

21240255 is a deficient number, since it is larger than the sum of its proper divisors (13574049).

21240255 is a wasteful number, since it uses less digits than its factorization.

21240255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34586.

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 21240255 is about 4608.7151137817. The cubic root of 21240255 is about 276.9405659954.

Adding to 21240255 its reverse (55204212), we get a palindrome (76444467).

The spelling of 21240255 in words is "twenty-one million, two hundred forty thousand, two hundred fifty-five".