21406829 has 4 divisors (see below), whose sum is σ = 21446940. Its totient is φ = 21366720.

The previous prime is 21406823. The next prime is 21406871. The reversal of 21406829 is 92860412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 10876804 + 10530025 = 3298^2 + 3245^2 .

It is a cyclic number.

It is not a de Polignac number, because 21406829 - 2²⁴ = 4629613 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21406795 and 21406804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21406823) 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, 19244 + ... + 20325.

It is an arithmetic number, because the mean of its divisors is an integer number (5361735).

Almost surely, 2^21406829 is an apocalyptic number.

It is an amenable number.

21406829 is a deficient number, since it is larger than the sum of its proper divisors (40111).

21406829 is an equidigital number, since it uses as much as digits as its factorization.

21406829 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40110.

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21406829 is about 4626.7514521530. The cubic root of 21406829 is about 277.6626387466.

The spelling of 21406829 in words is "twenty-one million, four hundred six thousand, eight hundred twenty-nine".