21236365878 has 96 divisors (see below), whose sum is σ = 53273777760. Its totient is φ = 5593835520.

The previous prime is 21236365867. The next prime is 21236365919. The reversal of 21236365878 is 87856363212.

It is a happy number.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 21236365878.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3547648 + ... + 3553628.

It is an arithmetic number, because the mean of its divisors is an integer number (554935185).

Almost surely, 2^21236365878 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21236365878, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26636888880).

21236365878 is an abundant number, since it is smaller than the sum of its proper divisors (32037411882).

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

21236365878 is a wasteful number, since it uses less digits than its factorization.

21236365878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6942 (or 6935 counting only the distinct ones).

The product of its digits is 2903040, while the sum is 51.

The spelling of 21236365878 in words is "twenty-one billion, two hundred thirty-six million, three hundred sixty-five thousand, eight hundred seventy-eight".