1990811681 has 2 divisors, whose sum is σ = 1990811682. Its totient is φ = 1990811680.

The previous prime is 1990811651. The next prime is 1990811699. The reversal of 1990811681 is 1861180991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1299963025 + 690848656 = 36055^2 + 26284^2 .

It is a cyclic number.

It is not a de Polignac number, because 1990811681 - 2⁶ = 1990811617 is a prime.

It is a super-2 number, since 2×1990811681² = 7926662298412091522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1990811651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995405840 + 995405841.

It is an arithmetic number, because the mean of its divisors is an integer number (995405841).

Almost surely, 2^1990811681 is an apocalyptic number.

It is an amenable number.

1990811681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1990811681 is an equidigital number, since it uses as much as digits as its factorization.

1990811681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31104, while the sum is 44.

The square root of 1990811681 is about 44618.5127609606. The cubic root of 1990811681 is about 1257.9886615465.

The spelling of 1990811681 in words is "one billion, nine hundred ninety million, eight hundred eleven thousand, six hundred eighty-one".