13781172661 has 2 divisors, whose sum is σ = 13781172662. Its totient is φ = 13781172660.

The previous prime is 13781172571. The next prime is 13781172673. The reversal of 13781172661 is 16627118731.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8339159761 + 5442012900 = 91319^2 + 73770^2 .

It is a cyclic number.

It is not a de Polignac number, because 13781172661 - 2²⁷ = 13646954933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (13781179661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6890586330 + 6890586331.

It is an arithmetic number, because the mean of its divisors is an integer number (6890586331).

Almost surely, 2^13781172661 is an apocalyptic number.

It is an amenable number.

13781172661 is a deficient number, since it is larger than the sum of its proper divisors (1).

13781172661 is an equidigital number, since it uses as much as digits as its factorization.

13781172661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 84672, while the sum is 43.

The spelling of 13781172661 in words is "thirteen billion, seven hundred eighty-one million, one hundred seventy-two thousand, six hundred sixty-one".