21117008640 has 864 divisors, whose sum is σ = 86318447040. Its totient is φ = 4359979008.

The previous prime is 21117008629. The next prime is 21117008681. The reversal of 21117008640 is 4680071112.

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 = 21117008598 and 21117008607.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 217701072 + ... + 217701168.

It is an arithmetic number, because the mean of its divisors is an integer number (99905610).

Almost surely, 2^21117008640 is an apocalyptic number.

21117008640 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 21117008640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43159223520).

21117008640 is an abundant number, since it is smaller than the sum of its proper divisors (65201438400).

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

21117008640 is a wasteful number, since it uses less digits than its factorization.

21117008640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 237 (or 216 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 30.

Adding to 21117008640 its reverse (4680071112), we get a palindrome (25797079752).

The spelling of 21117008640 in words is "twenty-one billion, one hundred seventeen million, eight thousand, six hundred forty".