21117021516 has 48 divisors (see below), whose sum is σ = 54877994080. Its totient is φ = 7022272320.

The previous prime is 21117021511. The next prime is 21117021517. The reversal of 21117021516 is 61512071112.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21117021516.

It is not an unprimeable number, because it can be changed into a prime (21117021511) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 186751 + ... + 277686.

Almost surely, 2^21117021516 is an apocalyptic number.

It is an amenable number.

21117021516 is an abundant number, since it is smaller than the sum of its proper divisors (33760972564).

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

21117021516 is a wasteful number, since it uses less digits than its factorization.

21117021516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 464871 (or 464863 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 27.

Adding to 21117021516 its reverse (61512071112), we get a palindrome (82629092628).

The spelling of 21117021516 in words is "twenty-one billion, one hundred seventeen million, twenty-one thousand, five hundred sixteen".