21398563 has 16 divisors (see below), whose sum is σ = 23560416. Its totient is φ = 19353600.

The previous prime is 21398561. The next prime is 21398569. The reversal of 21398563 is 36589312.

It is a cyclic number.

It is not a de Polignac number, because 21398563 - 2¹ = 21398561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21398561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53163 + ... + 53563.

It is an arithmetic number, because the mean of its divisors is an integer number (1472526).

Almost surely, 2^21398563 is an apocalyptic number.

21398563 is a deficient number, since it is larger than the sum of its proper divisors (2161853).

21398563 is a wasteful number, since it uses less digits than its factorization.

21398563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534.

The product of its digits is 38880, while the sum is 37.

The square root of 21398563 is about 4625.8580825615. The cubic root of 21398563 is about 277.6268954043.

The spelling of 21398563 in words is "twenty-one million, three hundred ninety-eight thousand, five hundred sixty-three".