21019783680 has 720 divisors, whose sum is σ = 86445627840. Its totient is φ = 4622598144.

The previous prime is 21019783679. The next prime is 21019783717. The reversal of 21019783680 is 8638791012.

21019783680 is a `hidden beast` number, since 210 + 1 + 9 + 78 + 368 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (720).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 356267491 + ... + 356267549.

It is an arithmetic number, because the mean of its divisors is an integer number (120063372).

Almost surely, 2^21019783680 is an apocalyptic number.

21019783680 is a gapful number since it is divisible by the number (20) 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 21019783680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43222813920).

21019783680 is an abundant number, since it is smaller than the sum of its proper divisors (65425844160).

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

21019783680 is an equidigital number, since it uses as much as digits as its factorization.

21019783680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189 (or 123 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The spelling of 21019783680 in words is "twenty-one billion, nineteen million, seven hundred eighty-three thousand, six hundred eighty".