21778326738 has 256 divisors, whose sum is σ = 58392576000. Its totient is φ = 5888510784.

The previous prime is 21778326721. The next prime is 21778326743. The reversal of 21778326738 is 83762387712.

It is a happy number.

21778326738 is a `hidden beast` number, since 217 + 78 + 326 + 7 + 38 = 666.

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

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 82807195 + ... + 82807457.

It is an arithmetic number, because the mean of its divisors is an integer number (228096000).

Almost surely, 2^21778326738 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21778326738, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29196288000).

21778326738 is an abundant number, since it is smaller than the sum of its proper divisors (36614249262).

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

21778326738 is a wasteful number, since it uses less digits than its factorization.

21778326738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 466 (or 460 counting only the distinct ones).

The product of its digits is 4741632, while the sum is 54.

The spelling of 21778326738 in words is "twenty-one billion, seven hundred seventy-eight million, three hundred twenty-six thousand, seven hundred thirty-eight".