21686361984 has 864 divisors, whose sum is σ = 82390426560. Its totient is φ = 5643509760.

The previous prime is 21686361971. The next prime is 21686361989. The reversal of 21686361984 is 48916368612.

21686361984 is a `hidden beast` number, since 2 + 16 + 8 + 6 + 3 + 619 + 8 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (864).

It is a super-2 number, since 2×21686361984² (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 a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21686361984.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21686361989) by changing a digit.

It is a polite number, since it can be written in 107 ways as a sum of consecutive naturals, for example, 699560049 + ... + 699560079.

It is an arithmetic number, because the mean of its divisors is an integer number (95359290).

Almost surely, 2^21686361984 is an apocalyptic number.

21686361984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21686361984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41195213280).

21686361984 is an abundant number, since it is smaller than the sum of its proper divisors (60704064576).

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

21686361984 is an frugal number, since it uses more digits than its factorization.

21686361984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100 (or 60 counting only the distinct ones).

The product of its digits is 2985984, while the sum is 54.

The spelling of 21686361984 in words is "twenty-one billion, six hundred eighty-six million, three hundred sixty-one thousand, nine hundred eighty-four".