21305170 has 16 divisors (see below), whose sum is σ = 38404440. Its totient is φ = 8509824.

The previous prime is 21305159. The next prime is 21305173. The reversal of 21305170 is 7150312.

It can be written as a sum of positive squares in 4 ways, for example, as 18671041 + 2634129 = 4321^2 + 1623^2 .

It is not an unprimeable number, because it can be changed into a prime (21305173) 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 7 ways as a sum of consecutive naturals, for example, 9694 + ... + 11686.

Almost surely, 2^21305170 is an apocalyptic number.

21305170 is a deficient number, since it is larger than the sum of its proper divisors (17099270).

21305170 is a wasteful number, since it uses less digits than its factorization.

21305170 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3069.

The product of its (nonzero) digits is 210, while the sum is 19.

The square root of 21305170 is about 4615.7523763738. The cubic root of 21305170 is about 277.2224099649. Note that the first 3 decimals are identical.

Adding to 21305170 its reverse (7150312), we get a palindrome (28455482).

The spelling of 21305170 in words is "twenty-one million, three hundred five thousand, one hundred seventy".