21978036201816 has 512 divisors, whose sum is σ = 70084362240000. Its totient is φ = 6346914900480.

The previous prime is 21978036201811. The next prime is 21978036201857. The reversal of 21978036201816 is 61810263087912.

21978036201816 is a `hidden beast` number, since 2 + 1 + 9 + 7 + 8 + 0 + 3 + 620 + 1 + 8 + 1 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21978036201811) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 173342941 + ... + 173469683.

It is an arithmetic number, because the mean of its divisors is an integer number (136883520000).

Almost surely, 2^{21978036201816} 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 21978036201816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35042181120000).

21978036201816 is an abundant number, since it is smaller than the sum of its proper divisors (48106326038184).

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

21978036201816 is a wasteful number, since it uses less digits than its factorization.

21978036201816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126884 (or 126874 counting only the distinct ones).

The product of its (nonzero) digits is 1741824, while the sum is 54.

The spelling of 21978036201816 in words is "twenty-one trillion, nine hundred seventy-eight billion, thirty-six million, two hundred one thousand, eight hundred sixteen".