21768666671 has 4 divisors (see below), whose sum is σ = 21796975200. Its totient is φ = 21740358144.

The previous prime is 21768666637. The next prime is 21768666679. The reversal of 21768666671 is 17666686712.

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 21768666671 - 2¹⁴ = 21768650287 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 (21768666679) 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, 14153111 + ... + 14154648.

It is an arithmetic number, because the mean of its divisors is an integer number (5449243800).

Almost surely, 2^21768666671 is an apocalyptic number.

21768666671 is a deficient number, since it is larger than the sum of its proper divisors (28308529).

21768666671 is an equidigital number, since it uses as much as digits as its factorization.

21768666671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28308528.

The product of its digits is 6096384, while the sum is 56.

The spelling of 21768666671 in words is "twenty-one billion, seven hundred sixty-eight million, six hundred sixty-six thousand, six hundred seventy-one".