21812129 has 8 divisors (see below), whose sum is σ = 22532328. Its totient is φ = 21098880.

The previous prime is 21812113. The next prime is 21812143. The reversal of 21812129 is 92121812.

It can be written as a sum of positive squares in 4 ways, for example, as 4631104 + 17181025 = 2152^2 + 4145^2 .

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

It is not a de Polignac number, because 21812129 - 2⁴ = 21812113 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21812098 and 21812107.

It is not an unprimeable number, because it can be changed into a prime (21812149) 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, 5069 + ... + 8325.

It is an arithmetic number, because the mean of its divisors is an integer number (2816541).

Almost surely, 2^21812129 is an apocalyptic number.

It is an amenable number.

21812129 is a deficient number, since it is larger than the sum of its proper divisors (720199).

21812129 is a wasteful number, since it uses less digits than its factorization.

21812129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3475.

The product of its digits is 576, while the sum is 26.

The square root of 21812129 is about 4670.3457045491. The cubic root of 21812129 is about 279.4040428278.

The spelling of 21812129 in words is "twenty-one million, eight hundred twelve thousand, one hundred twenty-nine".