20817879936 has 128 divisors (see below), whose sum is σ = 63659554560. Its totient is φ = 5904445440.

The previous prime is 20817879889. The next prime is 20817879937. The reversal of 20817879936 is 63997871802.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×20817879936² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20817879936.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20817879937) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 339991 + ... + 396521.

It is an arithmetic number, because the mean of its divisors is an integer number (497340270).

Almost surely, 2^20817879936 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20817879936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31829777280).

20817879936 is an abundant number, since it is smaller than the sum of its proper divisors (42841674624).

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

20817879936 is a wasteful number, since it uses less digits than its factorization.

20817879936 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56692 (or 56680 counting only the distinct ones).

The product of its (nonzero) digits is 9144576, while the sum is 60.

The spelling of 20817879936 in words is "twenty billion, eight hundred seventeen million, eight hundred seventy-nine thousand, nine hundred thirty-six".