21129085 has 12 divisors (see below), whose sum is σ = 25919388. Its totient is φ = 16534976.

The previous prime is 21129077. The next prime is 21129107. The reversal of 21129085 is 58092112.

It can be written as a sum of positive squares in 2 ways, for example, as 13439556 + 7689529 = 3666^2 + 2773^2 .

It is not a de Polignac number, because 21129085 - 2³ = 21129077 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10089 + ... + 12001.

It is an arithmetic number, because the mean of its divisors is an integer number (2159949).

Almost surely, 2^21129085 is an apocalyptic number.

It is an amenable number.

21129085 is a deficient number, since it is larger than the sum of its proper divisors (4790303).

21129085 is an equidigital number, since it uses as much as digits as its factorization.

21129085 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2012 (or 1965 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 21129085 is about 4596.6384456470. The cubic root of 21129085 is about 276.4565581116.

The spelling of 21129085 in words is "twenty-one million, one hundred twenty-nine thousand, eighty-five".