21777865871 has 4 divisors (see below), whose sum is σ = 22284327912. Its totient is φ = 21271403832.

The previous prime is 21777865841. The next prime is 21777865891. The reversal of 21777865871 is 17856877712.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21777865871 - 2⁶ = 21777865807 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21777865871.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21777865841) 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, 253230956 + ... + 253231041.

It is an arithmetic number, because the mean of its divisors is an integer number (5571081978).

Almost surely, 2^21777865871 is an apocalyptic number.

21777865871 is a deficient number, since it is larger than the sum of its proper divisors (506462041).

21777865871 is an equidigital number, since it uses as much as digits as its factorization.

21777865871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 506462040.

The product of its digits is 9219840, while the sum is 59.

The spelling of 21777865871 in words is "twenty-one billion, seven hundred seventy-seven million, eight hundred sixty-five thousand, eight hundred seventy-one".