21782181820 has 24 divisors (see below), whose sum is σ = 52277236704. Its totient is φ = 7468176576.

The previous prime is 21782181791. The next prime is 21782181877. The reversal of 21782181820 is 2818128712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77793367 + ... + 77793646.

It is an arithmetic number, because the mean of its divisors is an integer number (2178218196).

Almost surely, 2^21782181820 is an apocalyptic number.

21782181820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21782181820 is an abundant number, since it is smaller than the sum of its proper divisors (30495054884).

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

21782181820 is a wasteful number, since it uses less digits than its factorization.

21782181820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155587029 (or 155587027 counting only the distinct ones).

The product of its (nonzero) digits is 28672, while the sum is 40.

The spelling of 21782181820 in words is "twenty-one billion, seven hundred eighty-two million, one hundred eighty-one thousand, eight hundred twenty".