20917781500 has 144 divisors (see below), whose sum is σ = 57975057504. Its totient is φ = 6519744000.

The previous prime is 20917781491. The next prime is 20917781501. The reversal of 20917781500 is 518771902.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20917781501) 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 47 ways as a sum of consecutive naturals, for example, 230692 + ... + 308308.

It is an arithmetic number, because the mean of its divisors is an integer number (402604566).

Almost surely, 2^20917781500 is an apocalyptic number.

20917781500 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 20917781500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28987528752).

20917781500 is an abundant number, since it is smaller than the sum of its proper divisors (37057276004).

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

20917781500 is a wasteful number, since it uses less digits than its factorization.

20917781500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77661 (or 77642 counting only the distinct ones).

The product of its (nonzero) digits is 35280, while the sum is 40.

The spelling of 20917781500 in words is "twenty billion, nine hundred seventeen million, seven hundred eighty-one thousand, five hundred".