21409129 has 9 divisors (see below), whose sum is σ = 24942231. Its totient is φ = 18322920.

The previous prime is 21409123. The next prime is 21409133. The reversal of 21409129 is 92190412.

It is a happy number.

The square root of 21409129 is 4627.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 16999129 + 4410000 = 4123^2 + 2100^2 .

It is not a de Polignac number, because 21409129 - 2¹³ = 21400937 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21409097 and 21409106.

It is not an unprimeable number, because it can be changed into a prime (21409123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 32059 + ... + 32719.

It is an arithmetic number, because the mean of its divisors is an integer number (2771359).

Almost surely, 2^21409129 is an apocalyptic number.

21409129 is the 4627-th square number.

21409129 is the 2314-th centered octagonal number.

It is an amenable number.

21409129 is a deficient number, since it is larger than the sum of its proper divisors (3533102).

21409129 is an frugal number, since it uses more digits than its factorization.

21409129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1336 (or 668 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 28.

The cubic root of 21409129 is about 277.6725826325.

Multiplying 21409129 by its product of nonzero digits (1296), we get a square (27746231184 = 166572²).

The spelling of 21409129 in words is "twenty-one million, four hundred nine thousand, one hundred twenty-nine".