2221709779781 has 2 divisors, whose sum is σ = 2221709779782. Its totient is φ = 2221709779780.

The previous prime is 2221709779721. The next prime is 2221709779801. The reversal of 2221709779781 is 1879779071222.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2201157976900 + 20551802881 = 1483630^2 + 143359^2 .

It is a cyclic number.

It is not a de Polignac number, because 2221709779781 - 2³⁸ = 1946831872837 is a prime.

It is a super-2 number, since 2×2221709779781² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2221709779721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1110854889890 + 1110854889891.

It is an arithmetic number, because the mean of its divisors is an integer number (1110854889891).

Almost surely, 2^{2221709779781} is an apocalyptic number.

It is an amenable number.

2221709779781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2221709779781 is an equidigital number, since it uses as much as digits as its factorization.

2221709779781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12446784, while the sum is 62.

The spelling of 2221709779781 in words is "two trillion, two hundred twenty-one billion, seven hundred nine million, seven hundred seventy-nine thousand, seven hundred eighty-one".