21212481 has 8 divisors (see below), whose sum is σ = 29947104. Its totient is φ = 13309760.

The previous prime is 21212467. The next prime is 21212483. The reversal of 21212481 is 18421212.

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 21212481 - 2⁵ = 21212449 is a prime.

It is a super-2 number, since 2×21212481² = 899938700350722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21212483) 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 7 ways as a sum of consecutive naturals, for example, 207915 + ... + 208016.

It is an arithmetic number, because the mean of its divisors is an integer number (3743388).

Almost surely, 2^21212481 is an apocalyptic number.

It is an amenable number.

21212481 is a deficient number, since it is larger than the sum of its proper divisors (8734623).

21212481 is a wasteful number, since it uses less digits than its factorization.

21212481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415951.

The product of its digits is 256, while the sum is 21.

The square root of 21212481 is about 4605.7009238551. The cubic root of 21212481 is about 276.8198031276.

Adding to 21212481 its reverse (18421212), we get a palindrome (39633693).

The spelling of 21212481 in words is "twenty-one million, two hundred twelve thousand, four hundred eighty-one".