21386691771 has 4 divisors (see below), whose sum is σ = 28515589032. Its totient is φ = 14257794512.

The previous prime is 21386691769. The next prime is 21386691797. The reversal of 21386691771 is 17719668312.

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 21386691771 - 2¹ = 21386691769 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21386691971) 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, 3564448626 + ... + 3564448631.

It is an arithmetic number, because the mean of its divisors is an integer number (7128897258).

Almost surely, 2^21386691771 is an apocalyptic number.

21386691771 is a deficient number, since it is larger than the sum of its proper divisors (7128897261).

21386691771 is an equidigital number, since it uses as much as digits as its factorization.

21386691771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7128897260.

The product of its digits is 762048, while the sum is 51.

The spelling of 21386691771 in words is "twenty-one billion, three hundred eighty-six million, six hundred ninety-one thousand, seven hundred seventy-one".