21666161667 has 32 divisors (see below), whose sum is σ = 31305761280. Its totient is φ = 13287464960.

The previous prime is 21666161653. The next prime is 21666161689. The reversal of 21666161667 is 76616166612.

It is a cyclic number.

It is not a de Polignac number, because 21666161667 - 2⁶ = 21666161603 is a prime.

It is a super-2 number, since 2×21666161667² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21666161617) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 493192 + ... + 535322.

It is an arithmetic number, because the mean of its divisors is an integer number (978305040).

Almost surely, 2^21666161667 is an apocalyptic number.

21666161667 is a deficient number, since it is larger than the sum of its proper divisors (9639599613).

21666161667 is a wasteful number, since it uses less digits than its factorization.

21666161667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42443.

The product of its digits is 653184, while the sum is 48.

The spelling of 21666161667 in words is "twenty-one billion, six hundred sixty-six million, one hundred sixty-one thousand, six hundred sixty-seven".