21163631 has 4 divisors (see below), whose sum is σ = 21240312. Its totient is φ = 21086952.

The previous prime is 21163627. The next prime is 21163643. The reversal of 21163631 is 13636112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21163631 - 2² = 21163627 is a prime.

It is a super-2 number, since 2×21163631² = 895798554208322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21163597 and 21163606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21163601) 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, 37925 + ... + 38478.

It is an arithmetic number, because the mean of its divisors is an integer number (5310078).

Almost surely, 2^21163631 is an apocalyptic number.

21163631 is a deficient number, since it is larger than the sum of its proper divisors (76681).

21163631 is an equidigital number, since it uses as much as digits as its factorization.

21163631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76680.

The product of its digits is 648, while the sum is 23.

The square root of 21163631 is about 4600.3946569832. The cubic root of 21163631 is about 276.6071446606.

Adding to 21163631 its reverse (13636112), we get a palindrome (34799743).

The spelling of 21163631 in words is "twenty-one million, one hundred sixty-three thousand, six hundred thirty-one".