21409355 has 16 divisors (see below), whose sum is σ = 28322784. Its totient is φ = 15406080.

The previous prime is 21409321. The next prime is 21409357. The reversal of 21409355 is 55390412.

It is not a de Polignac number, because 21409355 - 2⁶ = 21409291 is a prime.

It is a Duffinian number.

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

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3329 + ... + 7341.

It is an arithmetic number, because the mean of its divisors is an integer number (1770174).

Almost surely, 2^21409355 is an apocalyptic number.

21409355 is a deficient number, since it is larger than the sum of its proper divisors (6913429).

21409355 is a wasteful number, since it uses less digits than its factorization.

21409355 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4126.

The product of its (nonzero) digits is 5400, while the sum is 29.

The square root of 21409355 is about 4627.0244218072. The cubic root of 21409355 is about 277.6735596890.

Adding to 21409355 its reverse (55390412), we get a palindrome (76799767).

The spelling of 21409355 in words is "twenty-one million, four hundred nine thousand, three hundred fifty-five".