21551255 has 16 divisors (see below), whose sum is σ = 28425600. Its totient is φ = 15555360.

The previous prime is 21551251. The next prime is 21551267. The reversal of 21551255 is 55215512.

It is not a de Polignac number, because 21551255 - 2² = 21551251 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551251) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6236 + ... + 9054.

It is an arithmetic number, because the mean of its divisors is an integer number (1776600).

Almost surely, 2^21551255 is an apocalyptic number.

21551255 is a deficient number, since it is larger than the sum of its proper divisors (6874345).

21551255 is a wasteful number, since it uses less digits than its factorization.

21551255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2974.

The product of its digits is 2500, while the sum is 26.

The square root of 21551255 is about 4642.3329264498. The cubic root of 21551255 is about 278.2856775553.

Adding to 21551255 its reverse (55215512), we get a palindrome (76766767).

The spelling of 21551255 in words is "twenty-one million, five hundred fifty-one thousand, two hundred fifty-five".