20817051840 has 336 divisors, whose sum is σ = 79969632288. Its totient is φ = 5123948544.

The previous prime is 20817051781. The next prime is 20817051847. The reversal of 20817051840 is 4815071802.

20817051840 is a `hidden beast` number, since 20 + 81 + 7 + 0 + 518 + 40 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 20817051795 and 20817051804.

It is not an unprimeable number, because it can be changed into a prime (20817051847) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1000584 + ... + 1021176.

It is an arithmetic number, because the mean of its divisors is an integer number (238004858).

Almost surely, 2^20817051840 is an apocalyptic number.

20817051840 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 20817051840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39984816144).

20817051840 is an abundant number, since it is smaller than the sum of its proper divisors (59152580448).

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

20817051840 is a wasteful number, since it uses less digits than its factorization.

20817051840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20638 (or 20616 counting only the distinct ones).

The product of its (nonzero) digits is 17920, while the sum is 36.

The spelling of 20817051840 in words is "twenty billion, eight hundred seventeen million, fifty-one thousand, eight hundred forty".