21013421 has 16 divisors (see below), whose sum is σ = 25764480. Its totient is φ = 16864320.

The previous prime is 21013417. The next prime is 21013423. The reversal of 21013421 is 12431012.

It is not a de Polignac number, because 21013421 - 2² = 21013417 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21013396 and 21013405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013423) 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 15 ways as a sum of consecutive naturals, for example, 95 + ... + 6483.

It is an arithmetic number, because the mean of its divisors is an integer number (1610280).

Almost surely, 2^21013421 is an apocalyptic number.

It is an amenable number.

21013421 is a deficient number, since it is larger than the sum of its proper divisors (4751059).

21013421 is a wasteful number, since it uses less digits than its factorization.

21013421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6436.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21013421 is about 4584.0398122180. The cubic root of 21013421 is about 275.9511789653.

Adding to 21013421 its reverse (12431012), we get a palindrome (33444433).

It can be divided in two parts, 210 and 13421, that added together give a palindrome (13631).

The spelling of 21013421 in words is "twenty-one million, thirteen thousand, four hundred twenty-one".