21212456 has 16 divisors (see below), whose sum is σ = 41145300. Its totient is φ = 10240384.

The previous prime is 21212453. The next prime is 21212461. The reversal of 21212456 is 65421212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20340100 + 872356 = 4510^2 + 934^2 .

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 (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45485 + ... + 45948.

Almost surely, 2^21212456 is an apocalyptic number.

It is an amenable number.

21212456 is a deficient number, since it is larger than the sum of its proper divisors (19932844).

21212456 is a wasteful number, since it uses less digits than its factorization.

21212456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91468 (or 91464 counting only the distinct ones).

The product of its digits is 960, while the sum is 23.

The square root of 21212456 is about 4605.6982098266. The cubic root of 21212456 is about 276.8196943787.

Adding to 21212456 its reverse (65421212), we get a palindrome (86633668).

The spelling of 21212456 in words is "twenty-one million, two hundred twelve thousand, four hundred fifty-six".