21216085 has 16 divisors (see below), whose sum is σ = 29408832. Its totient is φ = 14521600.

The previous prime is 21216073. The next prime is 21216127. The reversal of 21216085 is 58061212.

It is not a de Polignac number, because 21216085 - 2⁵ = 21216053 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 15 ways as a sum of consecutive naturals, for example, 10411 + ... + 12280.

It is an arithmetic number, because the mean of its divisors is an integer number (1838052).

Almost surely, 2^21216085 is an apocalyptic number.

It is an amenable number.

21216085 is a deficient number, since it is larger than the sum of its proper divisors (8192747).

21216085 is a wasteful number, since it uses less digits than its factorization.

21216085 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22724.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21216085 is about 4606.0921614748. The cubic root of 21216085 is about 276.8354794657.

Adding to 21216085 its reverse (58061212), we get a palindrome (79277297).

The spelling of 21216085 in words is "twenty-one million, two hundred sixteen thousand, eighty-five".