21187786761181 has 2 divisors, whose sum is σ = 21187786761182. Its totient is φ = 21187786761180.

The previous prime is 21187786761161. The next prime is 21187786761187. The reversal of 21187786761181 is 18116768778112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10607462748100 + 10580324013081 = 3256910^2 + 3252741^2 .

It is a cyclic number.

It is not a de Polignac number, because 21187786761181 - 2⁹ = 21187786760669 is a prime.

It is a super-2 number, since 2×21187786761181² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21187786761187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10593893380590 + 10593893380591.

It is an arithmetic number, because the mean of its divisors is an integer number (10593893380591).

Almost surely, 2^{21187786761181} is an apocalyptic number.

It is an amenable number.

21187786761181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21187786761181 is an equidigital number, since it uses as much as digits as its factorization.

21187786761181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12644352, while the sum is 64.

The spelling of 21187786761181 in words is "twenty-one trillion, one hundred eighty-seven billion, seven hundred eighty-six million, seven hundred sixty-one thousand, one hundred eighty-one".