21698 has 8 divisors (see below), whose sum is σ = 34320. Its totient is φ = 10260.

The previous prime is 21683. The next prime is 21701. The reversal of 21698 is 89612.

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

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

It is a Curzon number.

It is a plaindrome in base 15.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21698.

It is an unprimeable number.

21698 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 248 + ... + 323.

It is an arithmetic number, because the mean of its divisors is an integer number (4290).

2²¹⁶⁹⁸ is an apocalyptic number.

21698 is a deficient number, since it is larger than the sum of its proper divisors (12622).

21698 is a wasteful number, since it uses less digits than its factorization.

21698 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 592.

The product of its digits is 864, while the sum is 26.

The square root of 21698 is about 147.3024100278. The cubic root of 21698 is about 27.8915875855.

The spelling of 21698 in words is "twenty-one thousand, six hundred ninety-eight".