21381707780 has 12 divisors (see below), whose sum is σ = 44901586380. Its totient is φ = 8552683104.

The previous prime is 21381707773. The next prime is 21381707783. The reversal of 21381707780 is 8770718312.

It can be written as a sum of positive squares in 2 ways, for example, as 8386163776 + 12995544004 = 91576^2 + 113998^2 .

It is not an unprimeable number, because it can be changed into a prime (21381707783) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 534542675 + ... + 534542714.

It is an arithmetic number, because the mean of its divisors is an integer number (3741798865).

Almost surely, 2^21381707780 is an apocalyptic number.

21381707780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21381707780 is an abundant number, since it is smaller than the sum of its proper divisors (23519878600).

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

21381707780 is a wasteful number, since it uses less digits than its factorization.

21381707780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1069085398 (or 1069085396 counting only the distinct ones).

The product of its (nonzero) digits is 131712, while the sum is 44.

The spelling of 21381707780 in words is "twenty-one billion, three hundred eighty-one million, seven hundred seven thousand, seven hundred eighty".