21541213 has 2 divisors, whose sum is σ = 21541214. Its totient is φ = 21541212.

The previous prime is 21541211. The next prime is 21541217. The reversal of 21541213 is 31214512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19740249 + 1800964 = 4443^2 + 1342^2 .

It is a cyclic number.

It is not a de Polignac number, because 21541213 - 2¹ = 21541211 is a prime.

It is a super-2 number, since 2×21541213² = 928047715022738, which contains 22 as substring.

Together with 21541211, it forms a pair of twin primes.

It is equal to p_1362016 and since 21541213 and 1362016 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21541211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770606 + 10770607.

It is an arithmetic number, because the mean of its divisors is an integer number (10770607).

Almost surely, 2^21541213 is an apocalyptic number.

It is an amenable number.

21541213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21541213 is an equidigital number, since it uses as much as digits as its factorization.

21541213 is an evil number, because the sum of its binary digits is even.

The product of its digits is 240, while the sum is 19.

The square root of 21541213 is about 4641.2512321571. The cubic root of 21541213 is about 278.2424476068.

Adding to 21541213 its reverse (31214512), we get a palindrome (52755725).

The spelling of 21541213 in words is "twenty-one million, five hundred forty-one thousand, two hundred thirteen".