21129385 has 16 divisors (see below), whose sum is σ = 26963712. Its totient is φ = 15840000.

The previous prime is 21129379. The next prime is 21129403. The reversal of 21129385 is 58392112.

It is not a de Polignac number, because 21129385 - 2³ = 21129377 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27760 + ... + 28510.

It is an arithmetic number, because the mean of its divisors is an integer number (1685232).

Almost surely, 2^21129385 is an apocalyptic number.

It is an amenable number.

21129385 is a deficient number, since it is larger than the sum of its proper divisors (5834327).

21129385 is a wasteful number, since it uses less digits than its factorization.

21129385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1104.

The product of its digits is 4320, while the sum is 31.

The square root of 21129385 is about 4596.6710780738. The cubic root of 21129385 is about 276.4578665224.

The spelling of 21129385 in words is "twenty-one million, one hundred twenty-nine thousand, three hundred eighty-five".