21255231 has 8 divisors (see below), whose sum is σ = 29317680. Its totient is φ = 13681472.

The previous prime is 21255217. The next prime is 21255239. The reversal of 21255231 is 13255212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21255231 - 2⁷ = 21255103 is a prime.

It is a super-2 number, since 2×21255231² = 903569689726722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21255198 and 21255207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21255239) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 122070 + ... + 122243.

It is an arithmetic number, because the mean of its divisors is an integer number (3664710).

Almost surely, 2^21255231 is an apocalyptic number.

21255231 is a deficient number, since it is larger than the sum of its proper divisors (8062449).

21255231 is a wasteful number, since it uses less digits than its factorization.

21255231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244345.

The product of its digits is 600, while the sum is 21.

The square root of 21255231 is about 4610.3395753458. The cubic root of 21255231 is about 277.0056387788.

The spelling of 21255231 in words is "twenty-one million, two hundred fifty-five thousand, two hundred thirty-one".