21616806 has 16 divisors (see below), whose sum is σ = 44402544. Its totient is φ = 7010784.

The previous prime is 21616801. The next prime is 21616817. The reversal of 21616806 is 60861612.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21616801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48465 + ... + 48908.

It is an arithmetic number, because the mean of its divisors is an integer number (2775159).

Almost surely, 2^21616806 is an apocalyptic number.

21616806 is an abundant number, since it is smaller than the sum of its proper divisors (22785738).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21616806 is a wasteful number, since it uses less digits than its factorization.

21616806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97415.

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 21616806 is about 4649.3877016227. The cubic root of 21616806 is about 278.5675395719.

It can be divided in two parts, 21616 and 806, that added together give a palindrome (22422).

The spelling of 21616806 in words is "twenty-one million, six hundred sixteen thousand, eight hundred six".