21015013 has 2 divisors, whose sum is σ = 21015014. Its totient is φ = 21015012.

The previous prime is 21015011. The next prime is 21015017. The reversal of 21015013 is 31051012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20493729 + 521284 = 4527^2 + 722^2 .

It is a cyclic number.

It is not a de Polignac number, because 21015013 - 2¹ = 21015011 is a prime.

Together with 21015011, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21014984 and 21015002.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21015011) 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 as a sum of consecutive naturals, namely, 10507506 + 10507507.

It is an arithmetic number, because the mean of its divisors is an integer number (10507507).

Almost surely, 2^21015013 is an apocalyptic number.

It is an amenable number.

21015013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015013 is an equidigital number, since it uses as much as digits as its factorization.

21015013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30, while the sum is 13.

The square root of 21015013 is about 4584.2134548906. The cubic root of 21015013 is about 275.9581475781.

Adding to 21015013 its reverse (31051012), we get a palindrome (52066025).

The spelling of 21015013 in words is "twenty-one million, fifteen thousand, thirteen".