21309129 has 8 divisors (see below), whose sum is σ = 31569120. Its totient is φ = 14206068.

The previous prime is 21309107. The next prime is 21309133. The reversal of 21309129 is 92190312.

It is not a de Polignac number, because 21309129 - 2¹¹ = 21307081 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 789227 = 21309129 / (2 + 1 + 3 + 0 + 9 + 1 + 2 + 9).

It is not an unprimeable number, because it can be changed into a prime (21309179) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 394587 + ... + 394640.

It is an arithmetic number, because the mean of its divisors is an integer number (3946140).

Almost surely, 2^21309129 is an apocalyptic number.

It is an amenable number.

21309129 is a deficient number, since it is larger than the sum of its proper divisors (10259991).

21309129 is an equidigital number, since it uses as much as digits as its factorization.

21309129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 789236 (or 789230 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 21309129 is about 4616.1812139473. The cubic root of 21309129 is about 277.2395803754.

The spelling of 21309129 in words is "twenty-one million, three hundred nine thousand, one hundred twenty-nine".