261811397 has 2 divisors, whose sum is σ = 261811398. Its totient is φ = 261811396.

The previous prime is 261811343. The next prime is 261811409. The reversal of 261811397 is 793118162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 168766081 + 93045316 = 12991^2 + 9646^2 .

It is a cyclic number.

It is not a de Polignac number, because 261811397 - 2⁸ = 261811141 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261811397.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261811597) 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, 130905698 + 130905699.

It is an arithmetic number, because the mean of its divisors is an integer number (130905699).

Almost surely, 2^261811397 is an apocalyptic number.

It is an amenable number.

261811397 is a deficient number, since it is larger than the sum of its proper divisors (1).

261811397 is an equidigital number, since it uses as much as digits as its factorization.

261811397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 38.

The square root of 261811397 is about 16180.5870412665. The cubic root of 261811397 is about 639.7292124301.

The spelling of 261811397 in words is "two hundred sixty-one million, eight hundred eleven thousand, three hundred ninety-seven".