21543985100 has 72 divisors (see below), whose sum is σ = 51189390336. Its totient is φ = 7805160000.

The previous prime is 21543985081. The next prime is 21543985109. The reversal of 21543985100 is 158934512.

It is a happy number.

It is a hoax number, since the sum of its digits (38) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21543985109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 261965 + ... + 334235.

Almost surely, 2^21543985100 is an apocalyptic number.

21543985100 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 21543985100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25594695168).

21543985100 is an abundant number, since it is smaller than the sum of its proper divisors (29645405236).

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

21543985100 is a wasteful number, since it uses less digits than its factorization.

21543985100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72567 (or 72560 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 38.

The spelling of 21543985100 in words is "twenty-one billion, five hundred forty-three million, nine hundred eighty-five thousand, one hundred".