21505096800 has 864 divisors, whose sum is σ = 90084234240. Its totient is φ = 4769280000.

The previous prime is 21505096757. The next prime is 21505096801. The reversal of 21505096800 is 869050512.

It is a happy number.

21505096800 is a `hidden beast` number, since 21 + 50 + 509 + 6 + 80 + 0 = 666.

It is a super-3 number, since 3×21505096800³ (a number of 32 digits) contains 333 as substring.

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 (21505096801) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 46648570 + ... + 46649030.

It is an arithmetic number, because the mean of its divisors is an integer number (104264160).

Almost surely, 2^21505096800 is an apocalyptic number.

21505096800 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 21505096800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45042117120).

21505096800 is an abundant number, since it is smaller than the sum of its proper divisors (68579137440).

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

21505096800 is a wasteful number, since it uses less digits than its factorization.

21505096800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 548 (or 532 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The spelling of 21505096800 in words is "twenty-one billion, five hundred five million, ninety-six thousand, eight hundred".