21161165166560 has 96 divisors (see below), whose sum is σ = 51355556340480. Its totient is φ = 8233910710272.

The previous prime is 21161165166553. The next prime is 21161165166667. The reversal of 21161165166560 is 6566156116112.

It is a happy number.

It is a super-2 number, since 2×21161165166560² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27077612 + ... + 27848148.

It is an arithmetic number, because the mean of its divisors is an integer number (534953711880).

Almost surely, 2^{21161165166560} is an apocalyptic number.

21161165166560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21161165166560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25677778170240).

21161165166560 is an abundant number, since it is smaller than the sum of its proper divisors (30194391173920).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21161165166560 is a wasteful number, since it uses less digits than its factorization.

21161165166560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 775228 (or 775220 counting only the distinct ones).

The product of its (nonzero) digits is 388800, while the sum is 47.

The spelling of 21161165166560 in words is "twenty-one trillion, one hundred sixty-one billion, one hundred sixty-five million, one hundred sixty-six thousand, five hundred sixty".