21397863 has 8 divisors (see below), whose sum is σ = 28562800. Its totient is φ = 14249088.

The previous prime is 21397847. The next prime is 21397867. The reversal of 21397863 is 36879312.

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

It is not a de Polignac number, because 21397863 - 2⁴ = 21397847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21397867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 508 + ... + 6561.

It is an arithmetic number, because the mean of its divisors is an integer number (3570350).

Almost surely, 2^21397863 is an apocalyptic number.

21397863 is a deficient number, since it is larger than the sum of its proper divisors (7164937).

21397863 is a wasteful number, since it uses less digits than its factorization.

21397863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8081.

The product of its digits is 54432, while the sum is 39.

The square root of 21397863 is about 4625.7824203047. The cubic root of 21397863 is about 277.6238680834.

The spelling of 21397863 in words is "twenty-one million, three hundred ninety-seven thousand, eight hundred sixty-three".