21173741820 has 864 divisors, whose sum is σ = 86583893760. Its totient is φ = 4293596160.

The previous prime is 21173741789. The next prime is 21173741821. The reversal of 21173741820 is 2814737112.

21173741820 is a `hidden beast` number, since 211 + 7 + 3 + 7 + 418 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21173741821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 287 ways as a sum of consecutive naturals, for example, 154552792 + ... + 154552928.

It is an arithmetic number, because the mean of its divisors is an integer number (100212840).

Almost surely, 2^21173741820 is an apocalyptic number.

21173741820 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 21173741820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43291946880).

21173741820 is an abundant number, since it is smaller than the sum of its proper divisors (65410151940).

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

21173741820 is a wasteful number, since it uses less digits than its factorization.

21173741820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245 (or 224 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

The spelling of 21173741820 in words is "twenty-one billion, one hundred seventy-three million, seven hundred forty-one thousand, eight hundred twenty".