21629 has 4 divisors (see below), whose sum is σ = 22176. Its totient is φ = 21084.

The previous prime is 21617. The next prime is 21647. The reversal of 21629 is 92612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21629 - 2⁴ = 21613 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21629.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21649) 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, 209 + ... + 294.

It is an arithmetic number, because the mean of its divisors is an integer number (5544).

2²¹⁶²⁹ is an apocalyptic number.

It is an amenable number.

21629 is a deficient number, since it is larger than the sum of its proper divisors (547).

21629 is an equidigital number, since it uses as much as digits as its factorization.

21629 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546.

The product of its digits is 216, while the sum is 20.

The square root of 21629 is about 147.0680114777. The cubic root of 21629 is about 27.8619909536.

Subtracting from 21629 its sum of digits (20), we obtain a square (21609 = 147²).

The spelling of 21629 in words is "twenty-one thousand, six hundred twenty-nine".