21666516667 has 16 divisors (see below), whose sum is σ = 22090869504. Its totient is φ = 21246940000.

The previous prime is 21666516637. The next prime is 21666516671. The reversal of 21666516667 is 76661566612.

It is a cyclic number.

It is not a de Polignac number, because 21666516667 - 2²³ = 21658128059 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21666516607) 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, 8559192 + ... + 8561722.

It is an arithmetic number, because the mean of its divisors is an integer number (1380679344).

Almost surely, 2^21666516667 is an apocalyptic number.

21666516667 is a deficient number, since it is larger than the sum of its proper divisors (424352837).

21666516667 is a wasteful number, since it uses less digits than its factorization.

21666516667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3410.

The product of its digits is 3265920, while the sum is 52.

It can be divided in two parts, 216665 and 16667, that added together give a palindrome (233332).

The spelling of 21666516667 in words is "twenty-one billion, six hundred sixty-six million, five hundred sixteen thousand, six hundred sixty-seven".