21665116215 has 12 divisors (see below), whose sum is σ = 37552868184. Its totient is φ = 11554728624.

The previous prime is 21665116163. The next prime is 21665116219. The reversal of 21665116215 is 51261156612.

21665116215 is a `hidden beast` number, since 2 + 16 + 6 + 5 + 11 + 621 + 5 = 666.

It is not a de Polignac number, because 21665116215 - 2¹⁶ = 21665050679 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21665116215.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21665116219) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 240723469 + ... + 240723558.

It is an arithmetic number, because the mean of its divisors is an integer number (3129405682).

Almost surely, 2^21665116215 is an apocalyptic number.

21665116215 is a deficient number, since it is larger than the sum of its proper divisors (15887751969).

21665116215 is a wasteful number, since it uses less digits than its factorization.

21665116215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 481447038 (or 481447035 counting only the distinct ones).

The product of its digits is 21600, while the sum is 36.

The spelling of 21665116215 in words is "twenty-one billion, six hundred sixty-five million, one hundred sixteen thousand, two hundred fifteen".