21013405 has 24 divisors (see below), whose sum is σ = 29548800. Its totient is φ = 14303520.

The previous prime is 21013397. The next prime is 21013417. The reversal of 21013405 is 50431012.

It is not a de Polignac number, because 21013405 - 2³ = 21013397 is a prime.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 48540 + ... + 48970.

It is an arithmetic number, because the mean of its divisors is an integer number (1231200).

Almost surely, 2^21013405 is an apocalyptic number.

It is an amenable number.

21013405 is a deficient number, since it is larger than the sum of its proper divisors (8535395).

21013405 is a wasteful number, since it uses less digits than its factorization.

21013405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 649 (or 642 counting only the distinct ones).

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

The square root of 21013405 is about 4584.0380670322. The cubic root of 21013405 is about 275.9511089272.

Adding to 21013405 its reverse (50431012), we get a palindrome (71444417).

The spelling of 21013405 in words is "twenty-one million, thirteen thousand, four hundred five".