21779087761 has 4 divisors (see below), whose sum is σ = 21788330292. Its totient is φ = 21769845232.

The previous prime is 21779087749. The next prime is 21779087807. The reversal of 21779087761 is 16778097712.

It is a happy number.

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 3107505025 + 18671582736 = 55745^2 + 136644^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21779087761 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21779087461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4617730 + ... + 4622443.

It is an arithmetic number, because the mean of its divisors is an integer number (5447082573).

Almost surely, 2^21779087761 is an apocalyptic number.

It is an amenable number.

21779087761 is a deficient number, since it is larger than the sum of its proper divisors (9242531).

21779087761 is an equidigital number, since it uses as much as digits as its factorization.

21779087761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9242530.

The product of its (nonzero) digits is 2074464, while the sum is 55.

The spelling of 21779087761 in words is "twenty-one billion, seven hundred seventy-nine million, eighty-seven thousand, seven hundred sixty-one".