21505766500 has 48 divisors (see below), whose sum is σ = 47967978240. Its totient is φ = 8419269600.

The previous prime is 21505766467. The next prime is 21505766519. The reversal of 21505766500 is 566750512.

It is a self number, because there is not a number n which added to its sum of digits gives 21505766500.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 434070 + ... + 481069.

It is an arithmetic number, because the mean of its divisors is an integer number (999332880).

Almost surely, 2^21505766500 is an apocalyptic number.

21505766500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21505766500 is an abundant number, since it is smaller than the sum of its proper divisors (26462211740).

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

21505766500 is a wasteful number, since it uses less digits than its factorization.

21505766500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 915205 (or 915193 counting only the distinct ones).

The product of its (nonzero) digits is 63000, while the sum is 37.

The spelling of 21505766500 in words is "twenty-one billion, five hundred five million, seven hundred sixty-six thousand, five hundred".