21731568786 has 64 divisors (see below), whose sum is σ = 49339818240. Its totient is φ = 7087979520.

The previous prime is 21731568767. The next prime is 21731568799. The reversal of 21731568786 is 68786513712.

It is a happy number.

21731568786 is a `hidden beast` number, since 2 + 1 + 7 + 3 + 1 + 568 + 78 + 6 = 666.

It is a super-2 number, since 2×21731568786² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 618651 + ... + 652833.

It is an arithmetic number, because the mean of its divisors is an integer number (770934660).

Almost surely, 2^21731568786 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21731568786, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24669909120).

21731568786 is an abundant number, since it is smaller than the sum of its proper divisors (27608249454).

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

21731568786 is a wasteful number, since it uses less digits than its factorization.

21731568786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34448 (or 34442 counting only the distinct ones).

The product of its digits is 3386880, while the sum is 54.

The spelling of 21731568786 in words is "twenty-one billion, seven hundred thirty-one million, five hundred sixty-eight thousand, seven hundred eighty-six".