125781781 has 2 divisors, whose sum is σ = 125781782. Its totient is φ = 125781780.

The previous prime is 125781757. The next prime is 125781791. The reversal of 125781781 is 187187521.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 92948881 + 32832900 = 9641^2 + 5730^2 .

It is an emirp because it is prime and its reverse (187187521) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 125781781 - 2¹⁷ = 125650709 is a prime.

It is a super-2 number, since 2×125781781² = 31642112863063922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (125781791) 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, 62890890 + 62890891.

It is an arithmetic number, because the mean of its divisors is an integer number (62890891).

Almost surely, 2^125781781 is an apocalyptic number.

It is an amenable number.

125781781 is a deficient number, since it is larger than the sum of its proper divisors (1).

125781781 is an equidigital number, since it uses as much as digits as its factorization.

125781781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31360, while the sum is 40.

The square root of 125781781 is about 11215.2477012325. The cubic root of 125781781 is about 501.0402090960.

It can be divided in two parts, 1257 and 81781, that added together give a palindrome (83038).

The spelling of 125781781 in words is "one hundred twenty-five million, seven hundred eighty-one thousand, seven hundred eighty-one".