1921078811 has 2 divisors, whose sum is σ = 1921078812. Its totient is φ = 1921078810.

The previous prime is 1921078777. The next prime is 1921078849. The reversal of 1921078811 is 1188701291.

It is an a-pointer prime, because the next prime (1921078849) can be obtained adding 1921078811 to its sum of digits (38).

It is a weak prime.

It is an emirp because it is prime and its reverse (1188701291) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1921078811 - 2¹⁰ = 1921077787 is a prime.

It is not a weakly prime, because it can be changed into another prime (1921078891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 960539405 + 960539406.

It is an arithmetic number, because the mean of its divisors is an integer number (960539406).

Almost surely, 2^1921078811 is an apocalyptic number.

1921078811 is a deficient number, since it is larger than the sum of its proper divisors (1).

1921078811 is an equidigital number, since it uses as much as digits as its factorization.

1921078811 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 38.

The square root of 1921078811 is about 43830.1130616840. The cubic root of 1921078811 is about 1243.1257446713.

The spelling of 1921078811 in words is "one billion, nine hundred twenty-one million, seventy-eight thousand, eight hundred eleven".