21220513 has 4 divisors (see below), whose sum is σ = 22143168. Its totient is φ = 20297860.

The previous prime is 21220501. The next prime is 21220531. The reversal of 21220513 is 31502212.

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 a de Polignac number, because none of the positive numbers 2^k-21220513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21220583) 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 3 ways as a sum of consecutive naturals, for example, 461293 + ... + 461338.

It is an arithmetic number, because the mean of its divisors is an integer number (5535792).

Almost surely, 2^21220513 is an apocalyptic number.

21220513 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21220513 is a deficient number, since it is larger than the sum of its proper divisors (922655).

21220513 is an equidigital number, since it uses as much as digits as its factorization.

21220513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 922654.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21220513 is about 4606.5728041571. The cubic root of 21220513 is about 276.8547375307.

Adding to 21220513 its reverse (31502212), we get a palindrome (52722725).

The spelling of 21220513 in words is "twenty-one million, two hundred twenty thousand, five hundred thirteen".