21791365871 has 4 divisors (see below), whose sum is σ = 23772399144. Its totient is φ = 19810332600.

The previous prime is 21791365837. The next prime is 21791365873. The reversal of 21791365871 is 17856319712.

It is a happy number.

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-21791365871 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21791365873) 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, 990516620 + ... + 990516641.

It is an arithmetic number, because the mean of its divisors is an integer number (5943099786).

Almost surely, 2^21791365871 is an apocalyptic number.

21791365871 is a deficient number, since it is larger than the sum of its proper divisors (1981033273).

21791365871 is a wasteful number, since it uses less digits than its factorization.

21791365871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1981033272.

The product of its digits is 635040, while the sum is 50.

The spelling of 21791365871 in words is "twenty-one billion, seven hundred ninety-one million, three hundred sixty-five thousand, eight hundred seventy-one".