21042663 has 8 divisors (see below), whose sum is σ = 28142976. Its totient is φ = 13985400.

The previous prime is 21042649. The next prime is 21042689. The reversal of 21042663 is 36624012.

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

It is not a de Polignac number, because 21042663 - 2⁴ = 21042647 is a prime.

It is a super-2 number, since 2×21042663² = 885587332263138, which contains 22 as substring.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9603 + ... + 11588.

It is an arithmetic number, because the mean of its divisors is an integer number (3517872).

Almost surely, 2^21042663 is an apocalyptic number.

21042663 is a deficient number, since it is larger than the sum of its proper divisors (7100313).

21042663 is a wasteful number, since it uses less digits than its factorization.

21042663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21525.

The product of its (nonzero) digits is 1728, while the sum is 24.

The square root of 21042663 is about 4587.2282480818. The cubic root of 21042663 is about 276.0791229777.

Adding to 21042663 its reverse (36624012), we get a palindrome (57666675).

The spelling of 21042663 in words is "twenty-one million, forty-two thousand, six hundred sixty-three".