21161220013540 has 12 divisors (see below), whose sum is σ = 44438562028476. Its totient is φ = 8464488005408.

The previous prime is 21161220013499. The next prime is 21161220013567. The reversal of 21161220013540 is 4531002216112.

It can be written as a sum of positive squares in 2 ways, for example, as 15006930758884 + 6154289254656 = 3873878^2 + 2480784^2 .

It is a super-2 number, since 2×21161220013540² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21161220013499 and 21161220013508.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 529030500319 + ... + 529030500358.

It is an arithmetic number, because the mean of its divisors is an integer number (3703213502373).

Almost surely, 2^{21161220013540} is an apocalyptic number.

21161220013540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21161220013540 is an abundant number, since it is smaller than the sum of its proper divisors (23277342014936).

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

21161220013540 is a wasteful number, since it uses less digits than its factorization.

21161220013540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1058061000686 (or 1058061000684 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 28.

Adding to 21161220013540 its reverse (4531002216112), we get a palindrome (25692222229652).

The spelling of 21161220013540 in words is "twenty-one trillion, one hundred sixty-one billion, two hundred twenty million, thirteen thousand, five hundred forty".