21216845 has 16 divisors (see below), whose sum is σ = 28060032. Its totient is φ = 15301440.

The previous prime is 21216841. The next prime is 21216847. The reversal of 21216845 is 54861212.

It is not a de Polignac number, because 21216845 - 2² = 21216841 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216841) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1001 + ... + 6590.

It is an arithmetic number, because the mean of its divisors is an integer number (1753752).

Almost surely, 2^21216845 is an apocalyptic number.

It is an amenable number.

21216845 is a deficient number, since it is larger than the sum of its proper divisors (6843187).

21216845 is a wasteful number, since it uses less digits than its factorization.

21216845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7652.

The product of its digits is 3840, while the sum is 29.

The square root of 21216845 is about 4606.1746601708. The cubic root of 21216845 is about 276.8387850151.

The spelling of 21216845 in words is "twenty-one million, two hundred sixteen thousand, eight hundred forty-five".