21212421 has 8 divisors (see below), whose sum is σ = 28310304. Its totient is φ = 14128080.

The previous prime is 21212353. The next prime is 21212423. The reversal of 21212421 is 12421212.

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

It is not a de Polignac number, because 21212421 - 2⁹ = 21211909 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21212421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212423) 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, 1135 + ... + 6611.

It is an arithmetic number, because the mean of its divisors is an integer number (3538788).

Almost surely, 2^21212421 is an apocalyptic number.

It is an amenable number.

21212421 is a deficient number, since it is larger than the sum of its proper divisors (7097883).

21212421 is a wasteful number, since it uses less digits than its factorization.

21212421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6771.

The product of its digits is 64, while the sum is 15.

The square root of 21212421 is about 4605.6944101840. The cubic root of 21212421 is about 276.8195421302.

Adding to 21212421 its reverse (12421212), we get a palindrome (33633633).

The spelling of 21212421 in words is "twenty-one million, two hundred twelve thousand, four hundred twenty-one".