21680395 has 16 divisors (see below), whose sum is σ = 28988928. Its totient is φ = 15430240.

The previous prime is 21680381. The next prime is 21680413. The reversal of 21680395 is 59308612.

It is not a de Polignac number, because 21680395 - 2¹¹ = 21678347 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21680395.

It is an unprimeable number.

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, 1609 + ... + 6778.

It is an arithmetic number, because the mean of its divisors is an integer number (1811808).

Almost surely, 2^21680395 is an apocalyptic number.

21680395 is a deficient number, since it is larger than the sum of its proper divisors (7308533).

21680395 is a wasteful number, since it uses less digits than its factorization.

21680395 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8450.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 21680395 is about 4656.2211072929. The cubic root of 21680395 is about 278.8404212413.

The spelling of 21680395 in words is "twenty-one million, six hundred eighty thousand, three hundred ninety-five".