261891797 has 2 divisors, whose sum is σ = 261891798. Its totient is φ = 261891796.

The previous prime is 261891781. The next prime is 261891821. The reversal of 261891797 is 797198162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 226382116 + 35509681 = 15046^2 + 5959^2 .

It is a cyclic number.

It is not a de Polignac number, because 261891797 - 2⁴ = 261891781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261891197) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130945898 + 130945899.

It is an arithmetic number, because the mean of its divisors is an integer number (130945899).

Almost surely, 2^261891797 is an apocalyptic number.

It is an amenable number.

261891797 is a deficient number, since it is larger than the sum of its proper divisors (1).

261891797 is an equidigital number, since it uses as much as digits as its factorization.

261891797 is an evil number, because the sum of its binary digits is even.

The product of its digits is 381024, while the sum is 50.

The square root of 261891797 is about 16183.0713092416. The cubic root of 261891797 is about 639.7946908179.

The spelling of 261891797 in words is "two hundred sixty-one million, eight hundred ninety-one thousand, seven hundred ninety-seven".