991010001001 has 2 divisors, whose sum is σ = 991010001002. Its totient is φ = 991010001000.

The previous prime is 991010000999. The next prime is 991010001029. The reversal of 991010001001 is 100100010199.

991010001001 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 766367179776 + 224642821225 = 875424^2 + 473965^2 .

It is a cyclic number.

It is not a de Polignac number, because 991010001001 - 2¹ = 991010000999 is a prime.

Together with 991010000999, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (991010001101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495505000500 + 495505000501.

It is an arithmetic number, because the mean of its divisors is an integer number (495505000501).

Almost surely, 2^991010001001 is an apocalyptic number.

It is an amenable number.

991010001001 is a deficient number, since it is larger than the sum of its proper divisors (1).

991010001001 is an equidigital number, since it uses as much as digits as its factorization.

991010001001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 81, while the sum is 22.

The spelling of 991010001001 in words is "nine hundred ninety-one billion, ten million, one thousand, one".