21694 has 4 divisors (see below), whose sum is σ = 32544. Its totient is φ = 10846.

The previous prime is 21683. The next prime is 21701. The reversal of 21694 is 49612.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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

It is a nialpdrome in base 15.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5422 + ... + 5425.

It is an arithmetic number, because the mean of its divisors is an integer number (8136).

2²¹⁶⁹⁴ is an apocalyptic number.

21694 is a deficient number, since it is larger than the sum of its proper divisors (10850).

21694 is a wasteful number, since it uses less digits than its factorization.

21694 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10849.

The product of its digits is 432, while the sum is 22.

The square root of 21694 is about 147.2888318916. The cubic root of 21694 is about 27.8898735534.

The spelling of 21694 in words is "twenty-one thousand, six hundred ninety-four".