21778120838656 has 640 divisors, whose sum is σ = 57123699849216. Its totient is φ = 8059148697600.

The previous prime is 21778120838647. The next prime is 21778120838687. The reversal of 21778120838656 is 65683802187712.

It is a Harshad number since it is a multiple of its sum of digits (64).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 31067219106 + ... + 31067219806.

Almost surely, 2^{21778120838656} is an apocalyptic number.

21778120838656 is a gapful number since it is divisible by the number (26) 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 21778120838656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28561849924608).

21778120838656 is an abundant number, since it is smaller than the sum of its proper divisors (35345579010560).

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

21778120838656 is a wasteful number, since it uses less digits than its factorization.

21778120838656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1362 (or 1346 counting only the distinct ones).

The product of its (nonzero) digits is 54190080, while the sum is 64.

The spelling of 21778120838656 in words is "twenty-one trillion, seven hundred seventy-eight billion, one hundred twenty million, eight hundred thirty-eight thousand, six hundred fifty-six".