21105781789 has 8 divisors (see below), whose sum is σ = 21557271168. Its totient is φ = 20654393760.

The previous prime is 21105781787. The next prime is 21105781793. The reversal of 21105781789 is 98718750112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21105781789 - 2¹ = 21105781787 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105781783) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 519369 + ... + 558529.

It is an arithmetic number, because the mean of its divisors is an integer number (2694658896).

Almost surely, 2^21105781789 is an apocalyptic number.

It is an amenable number.

21105781789 is a deficient number, since it is larger than the sum of its proper divisors (451489379).

21105781789 is a wasteful number, since it uses less digits than its factorization.

21105781789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50675.

The product of its (nonzero) digits is 282240, while the sum is 49.

The spelling of 21105781789 in words is "twenty-one billion, one hundred five million, seven hundred eighty-one thousand, seven hundred eighty-nine".