21963 has 4 divisors (see below), whose sum is σ = 29288. Its totient is φ = 14640.

The previous prime is 21961. The next prime is 21977. The reversal of 21963 is 36912.

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

It is not a de Polignac number, because 21963 - 2¹ = 21961 is a prime.

It is a D-number.

It is a Duffinian number.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21961) 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, 3658 + ... + 3663.

It is an arithmetic number, because the mean of its divisors is an integer number (7322).

2²¹⁹⁶³ is an apocalyptic number.

21963 is a deficient number, since it is larger than the sum of its proper divisors (7325).

21963 is an equidigital number, since it uses as much as digits as its factorization.

21963 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7324.

The product of its digits is 324, while the sum is 21.

The square root of 21963 is about 148.1991902812. The cubic root of 21963 is about 28.0046760898.

It can be divided in two parts, 219 and 63, that added together give a palindrome (282).

The spelling of 21963 in words is "twenty-one thousand, nine hundred sixty-three".