21406545 has 16 divisors (see below), whose sum is σ = 38056320. Its totient is φ = 11416752.

The previous prime is 21406543. The next prime is 21406549. The reversal of 21406545 is 54560412.

21406545 is a `hidden beast` number, since 2 + 1 + 4 + 0 + 654 + 5 = 666.

It is not a de Polignac number, because 21406545 - 2¹ = 21406543 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21406543) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 79149 + ... + 79418.

It is an arithmetic number, because the mean of its divisors is an integer number (2378520).

Almost surely, 2^21406545 is an apocalyptic number.

It is an amenable number.

21406545 is a deficient number, since it is larger than the sum of its proper divisors (16649775).

21406545 is a wasteful number, since it uses less digits than its factorization.

21406545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158581 (or 158575 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

The square root of 21406545 is about 4626.7207609710. The cubic root of 21406545 is about 277.6614108434.

Adding to 21406545 its reverse (54560412), we get a palindrome (75966957).

The spelling of 21406545 in words is "twenty-one million, four hundred six thousand, five hundred forty-five".