261749861 has 2 divisors, whose sum is σ = 261749862. Its totient is φ = 261749860.

The previous prime is 261749849. The next prime is 261749869. The reversal of 261749861 is 168947162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 230736100 + 31013761 = 15190^2 + 5569^2 .

It is a cyclic number.

It is not a de Polignac number, because 261749861 - 2⁶ = 261749797 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 (261749869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130874930 + 130874931.

It is an arithmetic number, because the mean of its divisors is an integer number (130874931).

Almost surely, 2^261749861 is an apocalyptic number.

It is an amenable number.

261749861 is a deficient number, since it is larger than the sum of its proper divisors (1).

261749861 is an equidigital number, since it uses as much as digits as its factorization.

261749861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145152, while the sum is 44.

The square root of 261749861 is about 16178.6853915885. The cubic root of 261749861 is about 639.6790879742.

The spelling of 261749861 in words is "two hundred sixty-one million, seven hundred forty-nine thousand, eight hundred sixty-one".