21808577693 has 4 divisors (see below), whose sum is σ = 24924088800. Its totient is φ = 18693066588.

The previous prime is 21808577633. The next prime is 21808577699. The reversal of 21808577693 is 39677580812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21808577693 - 2¹⁶ = 21808512157 is a prime.

It is a super-2 number, since 2×21808577693² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21808577699) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1557755543 + ... + 1557755556.

It is an arithmetic number, because the mean of its divisors is an integer number (6231022200).

Almost surely, 2^21808577693 is an apocalyptic number.

It is an amenable number.

21808577693 is a deficient number, since it is larger than the sum of its proper divisors (3115511107).

21808577693 is an equidigital number, since it uses as much as digits as its factorization.

21808577693 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3115511106.

The product of its (nonzero) digits is 5080320, while the sum is 56.

The spelling of 21808577693 in words is "twenty-one billion, eight hundred eight million, five hundred seventy-seven thousand, six hundred ninety-three".