21181100640 has 384 divisors, whose sum is σ = 78498201600. Its totient is φ = 4798531584.

The previous prime is 21181100527. The next prime is 21181100657. The reversal of 21181100640 is 4600118112.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21181100640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 20908774 + ... + 20909786.

It is an arithmetic number, because the mean of its divisors is an integer number (204422400).

Almost surely, 2^21181100640 is an apocalyptic number.

21181100640 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 21181100640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39249100800).

21181100640 is an abundant number, since it is smaller than the sum of its proper divisors (57317100960).

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

21181100640 is a wasteful number, since it uses less digits than its factorization.

21181100640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1179 (or 1157 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 24.

Adding to 21181100640 its reverse (4600118112), we get a palindrome (25781218752).

The spelling of 21181100640 in words is "twenty-one billion, one hundred eighty-one million, one hundred thousand, six hundred forty".