21212455 has 32 divisors (see below), whose sum is σ = 29859840. Its totient is φ = 14302080.

The previous prime is 21212453. The next prime is 21212461. The reversal of 21212455 is 55421212.

It is not a de Polignac number, because 21212455 - 2¹ = 21212453 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212453) 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 31 ways as a sum of consecutive naturals, for example, 55194 + ... + 55576.

It is an arithmetic number, because the mean of its divisors is an integer number (933120).

Almost surely, 2^21212455 is an apocalyptic number.

21212455 is a deficient number, since it is larger than the sum of its proper divisors (8647385).

21212455 is a wasteful number, since it uses less digits than its factorization.

21212455 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 471.

The product of its digits is 800, while the sum is 22.

The square root of 21212455 is about 4605.6981012654. The cubic root of 21212455 is about 276.8196900288.

Adding to 21212455 its reverse (55421212), we get a palindrome (76633667).

The spelling of 21212455 in words is "twenty-one million, two hundred twelve thousand, four hundred fifty-five".