21413421 has 24 divisors (see below), whose sum is σ = 32979960. Its totient is φ = 13341696.

The previous prime is 21413393. The next prime is 21413423. The reversal of 21413421 is 12431412.

It can be written as a sum of positive squares in 4 ways, for example, as 15093225 + 6320196 = 3885^2 + 2514^2 .

It is not a de Polignac number, because 21413421 - 2⁵ = 21413389 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21413394 and 21413403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21413423) 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, 26065 + ... + 26873.

It is an arithmetic number, because the mean of its divisors is an integer number (1374165).

Almost surely, 2^21413421 is an apocalyptic number.

It is an amenable number.

21413421 is a deficient number, since it is larger than the sum of its proper divisors (11566539).

21413421 is a wasteful number, since it uses less digits than its factorization.

21413421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1005 (or 1002 counting only the distinct ones).

The product of its digits is 192, while the sum is 18.

The square root of 21413421 is about 4627.4637761953. The cubic root of 21413421 is about 277.6911368841.

Adding to 21413421 its reverse (12431412), we get a palindrome (33844833).

Subtracting from 21413421 its reverse (12431412), we obtain a square (8982009 = 2997²).

The spelling of 21413421 in words is "twenty-one million, four hundred thirteen thousand, four hundred twenty-one".