1001991161 has 2 divisors, whose sum is σ = 1001991162. Its totient is φ = 1001991160.

The previous prime is 1001991127. The next prime is 1001991173. The reversal of 1001991161 is 1611991001.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 657666025 + 344325136 = 25645^2 + 18556^2 .

It is an emirp because it is prime and its reverse (1611991001) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1001991161 - 2²² = 997796857 is a prime.

It is not a weakly prime, because it can be changed into another prime (1001991061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 500995580 + 500995581.

It is an arithmetic number, because the mean of its divisors is an integer number (500995581).

Almost surely, 2^1001991161 is an apocalyptic number.

It is an amenable number.

1001991161 is a deficient number, since it is larger than the sum of its proper divisors (1).

1001991161 is an equidigital number, since it uses as much as digits as its factorization.

1001991161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486, while the sum is 29.

The square root of 1001991161 is about 31654.2439650673. The cubic root of 1001991161 is about 1000.6632802953.

The spelling of 1001991161 in words is "one billion, one million, nine hundred ninety-one thousand, one hundred sixty-one".