991261 has 2 divisors, whose sum is σ = 991262. Its totient is φ = 991260.

The previous prime is 991229. The next prime is 991273. The reversal of 991261 is 162199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 962361 + 28900 = 981^2 + 170^2 .

It is a cyclic number.

It is not a de Polignac number, because 991261 - 2⁵ = 991229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495630 + 495631.

It is an arithmetic number, because the mean of its divisors is an integer number (495631).

2⁹⁹¹²⁶¹ is an apocalyptic number.

It is an amenable number.

991261 is a deficient number, since it is larger than the sum of its proper divisors (1).

991261 is an equidigital number, since it uses as much as digits as its factorization.

991261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 972, while the sum is 28.

The square root of 991261 is about 995.6209117932. The cubic root of 991261 is about 99.7078472992.

The spelling of 991261 in words is "nine hundred ninety-one thousand, two hundred sixty-one".