261891397 has 2 divisors, whose sum is σ = 261891398. Its totient is φ = 261891396.

The previous prime is 261891359. The next prime is 261891403. The reversal of 261891397 is 793198162.

It is a happy number.

261891397 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 228644641 + 33246756 = 15121^2 + 5766^2 .

It is a cyclic number.

It is not a de Polignac number, because 261891397 - 2¹¹ = 261889349 is a prime.

It is a super-2 number, since 2×261891397² = 137174207645223218, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261891347) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130945698 + 130945699.

It is an arithmetic number, because the mean of its divisors is an integer number (130945699).

Almost surely, 2^261891397 is an apocalyptic number.

It is an amenable number.

261891397 is a deficient number, since it is larger than the sum of its proper divisors (1).

261891397 is an equidigital number, since it uses as much as digits as its factorization.

261891397 is an evil number, because the sum of its binary digits is even.

The product of its digits is 163296, while the sum is 46.

The square root of 261891397 is about 16183.0589506434. The cubic root of 261891397 is about 639.7943650880.

The spelling of 261891397 in words is "two hundred sixty-one million, eight hundred ninety-one thousand, three hundred ninety-seven".