21006255 has 8 divisors (see below), whose sum is σ = 33610032. Its totient is φ = 11203328.

The previous prime is 21006247. The next prime is 21006257. The reversal of 21006255 is 55260012.

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 21006255 - 2³ = 21006247 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006257) 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, 700194 + ... + 700223.

It is an arithmetic number, because the mean of its divisors is an integer number (4201254).

Almost surely, 2^21006255 is an apocalyptic number.

21006255 is a deficient number, since it is larger than the sum of its proper divisors (12603777).

21006255 is a wasteful number, since it uses less digits than its factorization.

21006255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1400425.

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

The square root of 21006255 is about 4583.2581205950. The cubic root of 21006255 is about 275.9198070947.

Adding to 21006255 its reverse (55260012), we get a palindrome (76266267).

The spelling of 21006255 in words is "twenty-one million, six thousand, two hundred fifty-five".