21406434 has 48 divisors (see below), whose sum is σ = 52744608. Its totient is φ = 5755008.

The previous prime is 21406397. The next prime is 21406457. The reversal of 21406434 is 43460412.

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, 2857 + ... + 7139.

It is an arithmetic number, because the mean of its divisors is an integer number (1098846).

Almost surely, 2^21406434 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21406434, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26372304).

21406434 is an abundant number, since it is smaller than the sum of its proper divisors (31338174).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21406434 is a wasteful number, since it uses less digits than its factorization.

21406434 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4319 (or 4312 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 21406434 is about 4626.7087654185. The cubic root of 21406434 is about 277.6609309206.

Adding to 21406434 its reverse (43460412), we get a palindrome (64866846).

The spelling of 21406434 in words is "twenty-one million, four hundred six thousand, four hundred thirty-four".