21138085 has 8 divisors (see below), whose sum is σ = 25506936. Its totient is φ = 16816320.

The previous prime is 21138077. The next prime is 21138101. The reversal of 21138085 is 58083112.

It can be written as a sum of positive squares in 4 ways, for example, as 471969 + 20666116 = 687^2 + 4546^2 .

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

It is not a de Polignac number, because 21138085 - 2³ = 21138077 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 7 ways as a sum of consecutive naturals, for example, 10774 + ... + 12583.

It is an arithmetic number, because the mean of its divisors is an integer number (3188367).

Almost surely, 2^21138085 is an apocalyptic number.

It is an amenable number.

21138085 is a deficient number, since it is larger than the sum of its proper divisors (4368851).

21138085 is a wasteful number, since it uses less digits than its factorization.

21138085 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23543.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 21138085 is about 4597.6173176984. The cubic root of 21138085 is about 276.4958050522.

The spelling of 21138085 in words is "twenty-one million, one hundred thirty-eight thousand, eighty-five".