21993966878 has 16 divisors (see below), whose sum is σ = 35534518656. Its totient is φ = 10149403680.

The previous prime is 21993966853. The next prime is 21993966889. The reversal of 21993966878 is 87866939912.

It is a super-2 number, since 2×21993966878² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 101075 + ... + 232817.

It is an arithmetic number, because the mean of its divisors is an integer number (2220907416).

Almost surely, 2^21993966878 is an apocalyptic number.

21993966878 is a deficient number, since it is larger than the sum of its proper divisors (13540551778).

21993966878 is a wasteful number, since it uses less digits than its factorization.

21993966878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138179.

The product of its digits is 70543872, while the sum is 68.

The spelling of 21993966878 in words is "twenty-one billion, nine hundred ninety-three million, nine hundred sixty-six thousand, eight hundred seventy-eight".