21678305 has 16 divisors (see below), whose sum is σ = 29614464. Its totient is φ = 15079680.

The previous prime is 21678277. The next prime is 21678313. The reversal of 21678305 is 50387612.

It is a happy number.

It is not a de Polignac number, because 21678305 - 2⁸ = 21678049 is a prime.

It is an alternating number because its digits alternate between even and odd.

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, 7304 + ... + 9833.

It is an arithmetic number, because the mean of its divisors is an integer number (1850904).

Almost surely, 2^21678305 is an apocalyptic number.

It is an amenable number.

21678305 is a deficient number, since it is larger than the sum of its proper divisors (7936159).

21678305 is a wasteful number, since it uses less digits than its factorization.

21678305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17176.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 21678305 is about 4655.9966709610. The cubic root of 21678305 is about 278.8314608387.

The spelling of 21678305 in words is "twenty-one million, six hundred seventy-eight thousand, three hundred five".