21181721400 has 384 divisors, whose sum is σ = 83780352000. Its totient is φ = 4818424320.

The previous prime is 21181721383. The next prime is 21181721437. The reversal of 21181721400 is 412718112.

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

It is a congruent number.

It is an unprimeable number.

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 95 ways as a sum of consecutive naturals, for example, 8654977 + ... + 8657423.

It is an arithmetic number, because the mean of its divisors is an integer number (218178000).

Almost surely, 2^21181721400 is an apocalyptic number.

21181721400 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 21181721400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41890176000).

21181721400 is an abundant number, since it is smaller than the sum of its proper divisors (62598630600).

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

21181721400 is a wasteful number, since it uses less digits than its factorization.

21181721400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2708 (or 2693 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

The spelling of 21181721400 in words is "twenty-one billion, one hundred eighty-one million, seven hundred twenty-one thousand, four hundred".