21002013 has 24 divisors (see below), whose sum is σ = 32123520. Its totient is φ = 13194720.

The previous prime is 21001991. The next prime is 21002039. The reversal of 21002013 is 31020012.

It is a happy number.

It is not a de Polignac number, because 21002013 - 2¹² = 20997917 is a prime.

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

It is a junction number, because it is equal to n+sod(n) for n = 21001986 and 21002004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002083) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13983 + ... + 15411.

It is an arithmetic number, because the mean of its divisors is an integer number (1338480).

Almost surely, 2^21002013 is an apocalyptic number.

21002013 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21002013 is a deficient number, since it is larger than the sum of its proper divisors (11121507).

21002013 is a wasteful number, since it uses less digits than its factorization.

21002013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1529 (or 1526 counting only the distinct ones).

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

The square root of 21002013 is about 4582.7953259992. The cubic root of 21002013 is about 275.9012327761.

Adding to 21002013 its reverse (31020012), we get a palindrome (52022025).

The spelling of 21002013 in words is "twenty-one million, two thousand, thirteen".