21107785903 has 4 divisors (see below), whose sum is σ = 21124552680. Its totient is φ = 21091019128.

The previous prime is 21107785819. The next prime is 21107785931. The reversal of 21107785903 is 30958770112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21107785903 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21107785903.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21107789903) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8381500 + ... + 8384017.

It is an arithmetic number, because the mean of its divisors is an integer number (5281138170).

Almost surely, 2^21107785903 is an apocalyptic number.

21107785903 is a deficient number, since it is larger than the sum of its proper divisors (16766777).

21107785903 is a wasteful number, since it uses less digits than its factorization.

21107785903 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16766776.

The product of its (nonzero) digits is 105840, while the sum is 43.

It can be divided in two parts, 21 and 107785903, that added together give a square (107785924 = 10382²).

The spelling of 21107785903 in words is "twenty-one billion, one hundred seven million, seven hundred eighty-five thousand, nine hundred three".