21398 has 8 divisors (see below), whose sum is σ = 34608. Its totient is φ = 9864.

The previous prime is 21397. The next prime is 21401. The reversal of 21398 is 89312.

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

It is a Curzon number.

It is a nialpdrome in base 13.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21398.

It is not an unprimeable number, because it can be changed into a prime (21391) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 386 + ... + 437.

It is an arithmetic number, because the mean of its divisors is an integer number (4326).

2²¹³⁹⁸ is an apocalyptic number.

21398 is a deficient number, since it is larger than the sum of its proper divisors (13210).

21398 is a wasteful number, since it uses less digits than its factorization.

21398 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 838.

The product of its digits is 432, while the sum is 23.

The square root of 21398 is about 146.2805523643. The cubic root of 21398 is about 27.7624460579.

The spelling of 21398 in words is "twenty-one thousand, three hundred ninety-eight".