21685313 has 8 divisors (see below), whose sum is σ = 23486400. Its totient is φ = 19903248.

The previous prime is 21685309. The next prime is 21685333. The reversal of 21685313 is 31358612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21685313 - 2² = 21685309 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21685333) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2333 + ... + 6986.

It is an arithmetic number, because the mean of its divisors is an integer number (2935800).

Almost surely, 2^21685313 is an apocalyptic number.

It is an amenable number.

21685313 is a deficient number, since it is larger than the sum of its proper divisors (1801087).

21685313 is a wasteful number, since it uses less digits than its factorization.

21685313 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9511.

The product of its digits is 4320, while the sum is 29.

The square root of 21685313 is about 4656.7491880066. The cubic root of 21685313 is about 278.8615037833.

The spelling of 21685313 in words is "twenty-one million, six hundred eighty-five thousand, three hundred thirteen".