1991266649 has 2 divisors, whose sum is σ = 1991266650. Its totient is φ = 1991266648.

The previous prime is 1991266637. The next prime is 1991266723. The reversal of 1991266649 is 9466621991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1485331600 + 505935049 = 38540^2 + 22493^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1991266649 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1991266649.

It is not a weakly prime, because it can be changed into another prime (1991266619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995633324 + 995633325.

It is an arithmetic number, because the mean of its divisors is an integer number (995633325).

Almost surely, 2^1991266649 is an apocalyptic number.

It is an amenable number.

1991266649 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991266649 is an equidigital number, since it uses as much as digits as its factorization.

1991266649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1259712, while the sum is 53.

The square root of 1991266649 is about 44623.6108915448. The cubic root of 1991266649 is about 1258.0844852744.

The spelling of 1991266649 in words is "one billion, nine hundred ninety-one million, two hundred sixty-six thousand, six hundred forty-nine".