26166985721 has 2 divisors, whose sum is σ = 26166985722. Its totient is φ = 26166985720.

The previous prime is 26166985717. The next prime is 26166985727. The reversal of 26166985721 is 12758966162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 24379387321 + 1787598400 = 156139^2 + 42280^2 .

It is a cyclic number.

It is not a de Polignac number, because 26166985721 - 2² = 26166985717 is a prime.

It is a super-2 number, since 2×26166985721² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (26166985727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13083492860 + 13083492861.

It is an arithmetic number, because the mean of its divisors is an integer number (13083492861).

Almost surely, 2^26166985721 is an apocalyptic number.

It is an amenable number.

26166985721 is a deficient number, since it is larger than the sum of its proper divisors (1).

26166985721 is an equidigital number, since it uses as much as digits as its factorization.

26166985721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2177280, while the sum is 53.

The spelling of 26166985721 in words is "twenty-six billion, one hundred sixty-six million, nine hundred eighty-five thousand, seven hundred twenty-one".