21421213 has 4 divisors (see below), whose sum is σ = 23368608. Its totient is φ = 19473820.

The previous prime is 21421201. The next prime is 21421243. The reversal of 21421213 is 31212412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21421213 - 2¹⁷ = 21290141 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21421243) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 973681 + ... + 973702.

It is an arithmetic number, because the mean of its divisors is an integer number (5842152).

Almost surely, 2^21421213 is an apocalyptic number.

It is an amenable number.

21421213 is a deficient number, since it is larger than the sum of its proper divisors (1947395).

21421213 is a wasteful number, since it uses less digits than its factorization.

21421213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1947394.

The product of its digits is 96, while the sum is 16.

The square root of 21421213 is about 4628.3056294934. The cubic root of 21421213 is about 277.7248152477.

Adding to 21421213 its reverse (31212412), we get a palindrome (52633625).

The spelling of 21421213 in words is "twenty-one million, four hundred twenty-one thousand, two hundred thirteen".