21109599977 has 4 divisors (see below), whose sum is σ = 21109917060. Its totient is φ = 21109282896.

The previous prime is 21109599971. The next prime is 21109600003. The reversal of 21109599977 is 77999590112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 10576888336 + 10532711641 = 102844^2 + 102629^2 .

It is a cyclic number.

It is not a de Polignac number, because 21109599977 - 2⁶ = 21109599913 is a prime.

It is a super-2 number, since 2×21109599977² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21109599971) 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, 15902 + ... + 206087.

It is an arithmetic number, because the mean of its divisors is an integer number (5277479265).

Almost surely, 2^21109599977 is an apocalyptic number.

It is an amenable number.

21109599977 is a deficient number, since it is larger than the sum of its proper divisors (317083).

21109599977 is an equidigital number, since it uses as much as digits as its factorization.

21109599977 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 317082.

The product of its (nonzero) digits is 3214890, while the sum is 59.

The spelling of 21109599977 in words is "twenty-one billion, one hundred nine million, five hundred ninety-nine thousand, nine hundred seventy-seven".