266139721 has 2 divisors, whose sum is σ = 266139722. Its totient is φ = 266139720.

The previous prime is 266139719. The next prime is 266139787. The reversal of 266139721 is 127931662.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 249008400 + 17131321 = 15780^2 + 4139^2 .

It is a cyclic number.

It is not a de Polignac number, because 266139721 - 2¹ = 266139719 is a prime.

Together with 266139719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (266139701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 133069860 + 133069861.

It is an arithmetic number, because the mean of its divisors is an integer number (133069861).

Almost surely, 2^266139721 is an apocalyptic number.

It is an amenable number.

266139721 is a deficient number, since it is larger than the sum of its proper divisors (1).

266139721 is an equidigital number, since it uses as much as digits as its factorization.

266139721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 37.

The square root of 266139721 is about 16313.7892900454. The cubic root of 266139721 is about 643.2353431311.

The spelling of 266139721 in words is "two hundred sixty-six million, one hundred thirty-nine thousand, seven hundred twenty-one".