1981895291 has 2 divisors, whose sum is σ = 1981895292. Its totient is φ = 1981895290.

The previous prime is 1981895287. The next prime is 1981895299. The reversal of 1981895291 is 1925981891.

It is a weak prime.

It is an emirp because it is prime and its reverse (1925981891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1981895291 - 2² = 1981895287 is a prime.

It is not a weakly prime, because it can be changed into another prime (1981895299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990947645 + 990947646.

It is an arithmetic number, because the mean of its divisors is an integer number (990947646).

Almost surely, 2^1981895291 is an apocalyptic number.

1981895291 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981895291 is an equidigital number, since it uses as much as digits as its factorization.

1981895291 is an evil number, because the sum of its binary digits is even.

The product of its digits is 466560, while the sum is 53.

The square root of 1981895291 is about 44518.4825774644. The cubic root of 1981895291 is about 1256.1077695926.

The spelling of 1981895291 in words is "one billion, nine hundred eighty-one million, eight hundred ninety-five thousand, two hundred ninety-one".