21678355916 has 24 divisors (see below), whose sum is σ = 44365009920. Its totient is φ = 9074660112.

The previous prime is 21678355883. The next prime is 21678355931. The reversal of 21678355916 is 61955387612.

It is a happy number.

It is a super-2 number, since 2×21678355916² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9001436 + ... + 9003843.

It is an arithmetic number, because the mean of its divisors is an integer number (1848542080).

Almost surely, 2^21678355916 is an apocalyptic number.

It is an amenable number.

21678355916 is an abundant number, since it is smaller than the sum of its proper divisors (22686654004).

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

21678355916 is a wasteful number, since it uses less digits than its factorization.

21678355916 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18005333 (or 18005331 counting only the distinct ones).

The product of its digits is 2721600, while the sum is 53.

The spelling of 21678355916 in words is "twenty-one billion, six hundred seventy-eight million, three hundred fifty-five thousand, nine hundred sixteen".