21306545 has 16 divisors (see below), whose sum is σ = 27717312. Its totient is φ = 15629760.

The previous prime is 21306541. The next prime is 21306547. The reversal of 21306545 is 54560312.

It is not a de Polignac number, because 21306545 - 2² = 21306541 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21306541) 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, 9590 + ... + 11600.

It is an arithmetic number, because the mean of its divisors is an integer number (1732332).

Almost surely, 2^21306545 is an apocalyptic number.

It is an amenable number.

21306545 is a deficient number, since it is larger than the sum of its proper divisors (6410767).

21306545 is a wasteful number, since it uses less digits than its factorization.

21306545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2192.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21306545 is about 4615.9013204357. The cubic root of 21306545 is about 277.2283736600.

Adding to 21306545 its reverse (54560312), we get a palindrome (75866857).

The spelling of 21306545 in words is "twenty-one million, three hundred six thousand, five hundred forty-five".