21020013 has 16 divisors (see below), whose sum is σ = 35589760. Its totient is φ = 12011328.

The previous prime is 21020011. The next prime is 21020017. The reversal of 21020013 is 31002012.

It is a happy number.

It is not a de Polignac number, because 21020013 - 2¹ = 21020011 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21019977 and 21020004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 55420 + ... + 55797.

It is an arithmetic number, because the mean of its divisors is an integer number (2224360).

Almost surely, 2^21020013 is an apocalyptic number.

It is an amenable number.

21020013 is a deficient number, since it is larger than the sum of its proper divisors (14569747).

21020013 is a wasteful number, since it uses less digits than its factorization.

21020013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111233 (or 111227 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

The square root of 21020013 is about 4584.7587722802. The cubic root of 21020013 is about 275.9800316366.

Adding to 21020013 its reverse (31002012), we get a palindrome (52022025).

The spelling of 21020013 in words is "twenty-one million, twenty thousand, thirteen".