21206863878 has 16 divisors (see below), whose sum is σ = 42423284736. Its totient is φ = 7067361800.

The previous prime is 21206863837. The next prime is 21206863921. The reversal of 21206863878 is 87836860212.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21206863878.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 369198 + ... + 422753.

It is an arithmetic number, because the mean of its divisors is an integer number (2651455296).

Almost surely, 2^21206863878 is an apocalyptic number.

21206863878 is an abundant number, since it is smaller than the sum of its proper divisors (21216420858).

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

21206863878 is a wasteful number, since it uses less digits than its factorization.

21206863878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 796419.

The product of its (nonzero) digits is 1548288, while the sum is 51.

The spelling of 21206863878 in words is "twenty-one billion, two hundred six million, eight hundred sixty-three thousand, eight hundred seventy-eight".