21685329 has 12 divisors (see below), whose sum is σ = 31372432. Its totient is φ = 14434200.

The previous prime is 21685309. The next prime is 21685333. The reversal of 21685329 is 92358612.

It is not a de Polignac number, because 21685329 - 2¹³ = 21677137 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21685293 and 21685302.

It is not an unprimeable number, because it can be changed into a prime (21685309) 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 11 ways as a sum of consecutive naturals, for example, 5814 + ... + 8784.

Almost surely, 2^21685329 is an apocalyptic number.

It is an amenable number.

21685329 is a deficient number, since it is larger than the sum of its proper divisors (9687103).

21685329 is a wasteful number, since it uses less digits than its factorization.

21685329 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3788 (or 3785 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 21685329 is about 4656.7509059429. The cubic root of 21685329 is about 278.8615723671.

The spelling of 21685329 in words is "twenty-one million, six hundred eighty-five thousand, three hundred twenty-nine".