21106777777 has 2 divisors, whose sum is σ = 21106777778. Its totient is φ = 21106777776.

The previous prime is 21106777751. The next prime is 21106777807. The reversal of 21106777777 is 77777760112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13622624656 + 7484153121 = 116716^2 + 86511^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21106777777 is a prime.

It is a super-2 number, since 2×21106777777² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21106777877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10553388888 + 10553388889.

It is an arithmetic number, because the mean of its divisors is an integer number (10553388889).

Almost surely, 2^21106777777 is an apocalyptic number.

It is an amenable number.

21106777777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21106777777 is an equidigital number, since it uses as much as digits as its factorization.

21106777777 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1411788, while the sum is 52.

The spelling of 21106777777 in words is "twenty-one billion, one hundred six million, seven hundred seventy-seven thousand, seven hundred seventy-seven".