21013863 has 8 divisors (see below), whose sum is σ = 30173808. Its totient is φ = 12931584.

The previous prime is 21013859. The next prime is 21013871. The reversal of 21013863 is 36831012.

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

It is not a de Polignac number, because 21013863 - 2² = 21013859 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013823) 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, 269370 + ... + 269447.

It is an arithmetic number, because the mean of its divisors is an integer number (3771726).

Almost surely, 2^21013863 is an apocalyptic number.

21013863 is a deficient number, since it is larger than the sum of its proper divisors (9159945).

21013863 is a wasteful number, since it uses less digits than its factorization.

21013863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 538833.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21013863 is about 4584.0880227151. The cubic root of 21013863 is about 275.9531137536.

Adding to 21013863 its reverse (36831012), we get a palindrome (57844875).

The spelling of 21013863 in words is "twenty-one million, thirteen thousand, eight hundred sixty-three".