21409356 has 24 divisors (see below), whose sum is σ = 51118144. Its totient is φ = 6970320.

The previous prime is 21409321. The next prime is 21409357. The reversal of 21409356 is 65390412.

It is not an unprimeable number, because it can be changed into a prime (21409357) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20230 + ... + 21261.

Almost surely, 2^21409356 is an apocalyptic number.

It is an amenable number.

21409356 is an abundant number, since it is smaller than the sum of its proper divisors (29708788).

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

21409356 is a wasteful number, since it uses less digits than its factorization.

21409356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41541 (or 41539 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 21409356 is about 4627.0245298680. The cubic root of 21409356 is about 277.6735640122.

Adding to 21409356 its reverse (65390412), we get a palindrome (86799768).

The spelling of 21409356 in words is "twenty-one million, four hundred nine thousand, three hundred fifty-six".