261766621 has 2 divisors, whose sum is σ = 261766622. Its totient is φ = 261766620.

The previous prime is 261766597. The next prime is 261766679. The reversal of 261766621 is 126667162.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 163558521 + 98208100 = 12789^2 + 9910^2 .

It is a cyclic number.

It is not a de Polignac number, because 261766621 - 2¹³ = 261758429 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261766691) 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, 130883310 + 130883311.

It is an arithmetic number, because the mean of its divisors is an integer number (130883311).

Almost surely, 2^261766621 is an apocalyptic number.

It is an amenable number.

261766621 is a deficient number, since it is larger than the sum of its proper divisors (1).

261766621 is an equidigital number, since it uses as much as digits as its factorization.

261766621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 37.

The square root of 261766621 is about 16179.2033487437. The cubic root of 261766621 is about 639.6927406943.

The spelling of 261766621 in words is "two hundred sixty-one million, seven hundred sixty-six thousand, six hundred twenty-one".