21408345 has 96 divisors (see below), whose sum is σ = 46176000. Its totient is φ = 9144576.

The previous prime is 21408341. The next prime is 21408347. The reversal of 21408345 is 54380412.

It is not a de Polignac number, because 21408345 - 2² = 21408341 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21408341) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 293229 + ... + 293301.

It is an arithmetic number, because the mean of its divisors is an integer number (481000).

Almost surely, 2^21408345 is an apocalyptic number.

It is an amenable number.

21408345 is an abundant number, since it is smaller than the sum of its proper divisors (24767655).

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

21408345 is a wasteful number, since it uses less digits than its factorization.

21408345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124 (or 107 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 21408345 is about 4626.9152791033. The cubic root of 21408345 is about 277.6691931445.

Adding to 21408345 its reverse (54380412), we get a palindrome (75788757).

The spelling of 21408345 in words is "twenty-one million, four hundred eight thousand, three hundred forty-five".