21408475 has 12 divisors (see below), whose sum is σ = 28960200. Its totient is φ = 15569600.

The previous prime is 21408473. The next prime is 21408479. The reversal of 21408475 is 57480412.

It is not a de Polignac number, because 21408475 - 2¹ = 21408473 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21408473) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 38650 + ... + 39199.

It is an arithmetic number, because the mean of its divisors is an integer number (2413350).

Almost surely, 2^21408475 is an apocalyptic number.

21408475 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21408475 is a deficient number, since it is larger than the sum of its proper divisors (7551725).

21408475 is a wasteful number, since it uses less digits than its factorization.

21408475 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77870 (or 77865 counting only the distinct ones).

The product of its (nonzero) digits is 8960, while the sum is 31.

The square root of 21408475 is about 4626.9293273185. The cubic root of 21408475 is about 277.6697551827.

Adding to 21408475 its reverse (57480412), we get a palindrome (78888887).

The spelling of 21408475 in words is "twenty-one million, four hundred eight thousand, four hundred seventy-five".