991158061 has 2 divisors, whose sum is σ = 991158062. Its totient is φ = 991158060.

The previous prime is 991158017. The next prime is 991158097. The reversal of 991158061 is 160851199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 931775625 + 59382436 = 30525^2 + 7706^2 .

It is an emirp because it is prime and its reverse (160851199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991158061 - 2¹⁵ = 991125293 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991158661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495579030 + 495579031.

It is an arithmetic number, because the mean of its divisors is an integer number (495579031).

Almost surely, 2^991158061 is an apocalyptic number.

It is an amenable number.

991158061 is a deficient number, since it is larger than the sum of its proper divisors (1).

991158061 is an equidigital number, since it uses as much as digits as its factorization.

991158061 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19440, while the sum is 40.

The square root of 991158061 is about 31482.6628638684. The cubic root of 991158061 is about 997.0439574224.

The spelling of 991158061 in words is "nine hundred ninety-one million, one hundred fifty-eight thousand, sixty-one".