21168158861 has 4 divisors (see below), whose sum is σ = 21172887324. Its totient is φ = 21163430400.

The previous prime is 21168158849. The next prime is 21168158863. The reversal of 21168158861 is 16885186112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15249780100 + 5918378761 = 123490^2 + 76931^2 .

It is a cyclic number.

It is not a de Polignac number, because 21168158861 - 2¹⁴ = 21168142477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21168158863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2357510 + ... + 2366471.

It is an arithmetic number, because the mean of its divisors is an integer number (5293221831).

Almost surely, 2^21168158861 is an apocalyptic number.

It is an amenable number.

21168158861 is a deficient number, since it is larger than the sum of its proper divisors (4728463).

21168158861 is an equidigital number, since it uses as much as digits as its factorization.

21168158861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4728462.

The product of its digits is 184320, while the sum is 47.

The spelling of 21168158861 in words is "twenty-one billion, one hundred sixty-eight million, one hundred fifty-eight thousand, eight hundred sixty-one".