21678355917 has 32 divisors (see below), whose sum is σ = 32689776000. Its totient is φ = 14195326464.

The previous prime is 21678355883. The next prime is 21678355931. The reversal of 21678355917 is 71955387612.

21678355917 is a `hidden beast` number, since 2 + 1 + 6 + 7 + 83 + 559 + 1 + 7 = 666.

It is not a de Polignac number, because 21678355917 - 2¹¹ = 21678353869 is a prime.

It is a super-2 number, since 2×21678355917² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21678355997) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 614173 + ... + 648509.

It is an arithmetic number, because the mean of its divisors is an integer number (1021555500).

Almost surely, 2^21678355917 is an apocalyptic number.

21678355917 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21678355917 is a deficient number, since it is larger than the sum of its proper divisors (11011420083).

21678355917 is a wasteful number, since it uses less digits than its factorization.

21678355917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34762 (or 34756 counting only the distinct ones).

The product of its digits is 3175200, while the sum is 54.

The spelling of 21678355917 in words is "twenty-one billion, six hundred seventy-eight million, three hundred fifty-five thousand, nine hundred seventeen".