21512213 has 2 divisors, whose sum is σ = 21512214. Its totient is φ = 21512212.

The previous prime is 21512147. The next prime is 21512263. The reversal of 21512213 is 31221512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21464689 + 47524 = 4633^2 + 218^2 .

It is a cyclic number.

It is not a de Polignac number, because 21512213 - 2⁸ = 21511957 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21512191 and 21512200.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21512263) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756106 + 10756107.

It is an arithmetic number, because the mean of its divisors is an integer number (10756107).

Almost surely, 2^21512213 is an apocalyptic number.

It is an amenable number.

21512213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21512213 is an equidigital number, since it uses as much as digits as its factorization.

21512213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 120, while the sum is 17.

The square root of 21512213 is about 4638.1260224362. The cubic root of 21512213 is about 278.1175296230.

Adding to 21512213 its reverse (31221512), we get a palindrome (52733725).

The spelling of 21512213 in words is "twenty-one million, five hundred twelve thousand, two hundred thirteen".