21665511006667 has 8 divisors (see below), whose sum is σ = 23869113837552. Its totient is φ = 19500909996000.

The previous prime is 21665511006649. The next prime is 21665511006679. The reversal of 21665511006667 is 76660011556612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21665511006667 - 2³¹ = 21663363523019 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21665511006367) 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, 9750453888 + ... + 9750456109.

It is an arithmetic number, because the mean of its divisors is an integer number (2983639229694).

Almost surely, 2^{21665511006667} is an apocalyptic number.

21665511006667 is a deficient number, since it is larger than the sum of its proper divisors (2203602830885).

21665511006667 is a wasteful number, since it uses less digits than its factorization.

21665511006667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19500910109.

The product of its (nonzero) digits is 2721600, while the sum is 52.

Subtracting 21665511006667 from its reverse (76660011556612), we obtain a palindrome (54994500549945).

The spelling of 21665511006667 in words is "twenty-one trillion, six hundred sixty-five billion, five hundred eleven million, six thousand, six hundred sixty-seven".