21117117540 has 96 divisors (see below), whose sum is σ = 62187181056. Its totient is φ = 5346731520.

The previous prime is 21117117533. The next prime is 21117117563. The reversal of 21117117540 is 4571171112.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21117117498 and 21117117507.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8527 + ... + 205686.

It is an arithmetic number, because the mean of its divisors is an integer number (647783136).

Almost surely, 2^21117117540 is an apocalyptic number.

21117117540 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 21117117540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31093590528).

21117117540 is an abundant number, since it is smaller than the sum of its proper divisors (41070063516).

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

21117117540 is a wasteful number, since it uses less digits than its factorization.

21117117540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214309 (or 214307 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 30.

Adding to 21117117540 its reverse (4571171112), we get a palindrome (25688288652).

It can be divided in two parts, 2111 and 7117540, that added together give a triangular number (7119651 = T₃₇₇₃).

The spelling of 21117117540 in words is "twenty-one billion, one hundred seventeen million, one hundred seventeen thousand, five hundred forty".