21782137680 has 400 divisors, whose sum is σ = 77294606400. Its totient is φ = 5684152320.

The previous prime is 21782137669. The next prime is 21782137717. The reversal of 21782137680 is 8673128712.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 103232775 + ... + 103232985.

It is an arithmetic number, because the mean of its divisors is an integer number (193236516).

Almost surely, 2^21782137680 is an apocalyptic number.

21782137680 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 21782137680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38647303200).

21782137680 is an abundant number, since it is smaller than the sum of its proper divisors (55512468720).

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

21782137680 is a wasteful number, since it uses less digits than its factorization.

21782137680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 504 (or 489 counting only the distinct ones).

The product of its (nonzero) digits is 225792, while the sum is 45.

The spelling of 21782137680 in words is "twenty-one billion, seven hundred eighty-two million, one hundred thirty-seven thousand, six hundred eighty".