21680145 has 24 divisors (see below), whose sum is σ = 39214656. Its totient is φ = 11059488.

The previous prime is 21680143. The next prime is 21680149. The reversal of 21680145 is 54108612.

It is not a de Polignac number, because 21680145 - 2¹ = 21680143 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21680143) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9439 + ... + 11508.

It is an arithmetic number, because the mean of its divisors is an integer number (1633944).

Almost surely, 2^21680145 is an apocalyptic number.

It is an amenable number.

21680145 is a deficient number, since it is larger than the sum of its proper divisors (17534511).

21680145 is a wasteful number, since it uses less digits than its factorization.

21680145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20981 (or 20978 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21680145 is about 4656.1942614114. The cubic root of 21680145 is about 278.8393494532.

Adding to 21680145 its reverse (54108612), we get a palindrome (75788757).

The spelling of 21680145 in words is "twenty-one million, six hundred eighty thousand, one hundred forty-five".