1991964517 has 2 divisors, whose sum is σ = 1991964518. Its totient is φ = 1991964516.

The previous prime is 1991964509. The next prime is 1991964529. The reversal of 1991964517 is 7154691991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1783710756 + 208253761 = 42234^2 + 14431^2 .

It is an emirp because it is prime and its reverse (7154691991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1991964517 - 2³ = 1991964509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991964217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995982258 + 995982259.

It is an arithmetic number, because the mean of its divisors is an integer number (995982259).

Almost surely, 2^1991964517 is an apocalyptic number.

It is an amenable number.

1991964517 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991964517 is an equidigital number, since it uses as much as digits as its factorization.

1991964517 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 612360, while the sum is 52.

The square root of 1991964517 is about 44631.4296992601. The cubic root of 1991964517 is about 1258.2314393681.

The spelling of 1991964517 in words is "one billion, nine hundred ninety-one million, nine hundred sixty-four thousand, five hundred seventeen".