21761969785 has 4 divisors (see below), whose sum is σ = 26114363748. Its totient is φ = 17409575824.

The previous prime is 21761969767. The next prime is 21761969819. The reversal of 21761969785 is 58796916712.

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 9815261184 + 11946708601 = 99072^2 + 109301^2 .

It is a cyclic number.

It is not a de Polignac number, because 21761969785 - 2²³ = 21753581177 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2176196974 + ... + 2176196983.

It is an arithmetic number, because the mean of its divisors is an integer number (6528590937).

Almost surely, 2^21761969785 is an apocalyptic number.

It is an amenable number.

21761969785 is a deficient number, since it is larger than the sum of its proper divisors (4352393963).

21761969785 is an equidigital number, since it uses as much as digits as its factorization.

21761969785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4352393962.

The product of its digits is 11430720, while the sum is 61.

The spelling of 21761969785 in words is "twenty-one billion, seven hundred sixty-one million, nine hundred sixty-nine thousand, seven hundred eighty-five".