1991518783 has 2 divisors, whose sum is σ = 1991518784. Its totient is φ = 1991518782.

The previous prime is 1991518759. The next prime is 1991518799. The reversal of 1991518783 is 3878151991.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1991518783 - 2¹⁷ = 1991387711 is a prime.

It is a super-2 number, since 2×1991518783² = 7932294126083602178, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1991518783.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991558783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995759391 + 995759392.

It is an arithmetic number, because the mean of its divisors is an integer number (995759392).

Almost surely, 2^1991518783 is an apocalyptic number.

1991518783 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991518783 is an equidigital number, since it uses as much as digits as its factorization.

1991518783 is an evil number, because the sum of its binary digits is even.

The product of its digits is 544320, while the sum is 52.

The square root of 1991518783 is about 44626.4359208754. The cubic root of 1991518783 is about 1258.1375825474.

The spelling of 1991518783 in words is "one billion, nine hundred ninety-one million, five hundred eighteen thousand, seven hundred eighty-three".