21257255 has 4 divisors (see below), whose sum is σ = 25508712. Its totient is φ = 17005800.

The previous prime is 21257251. The next prime is 21257273. The reversal of 21257255 is 55275212.

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

It is not a de Polignac number, because 21257255 - 2² = 21257251 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21257251) 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, 2125721 + ... + 2125730.

It is an arithmetic number, because the mean of its divisors is an integer number (6377178).

Almost surely, 2^21257255 is an apocalyptic number.

21257255 is a deficient number, since it is larger than the sum of its proper divisors (4251457).

21257255 is an equidigital number, since it uses as much as digits as its factorization.

21257255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4251456.

The product of its digits is 7000, while the sum is 29.

The square root of 21257255 is about 4610.5590767281. The cubic root of 21257255 is about 277.0144309928.

It can be divided in two parts, 21257 and 255, that added together give a palindrome (21512).

The spelling of 21257255 in words is "twenty-one million, two hundred fifty-seven thousand, two hundred fifty-five".