1981209077 has 2 divisors, whose sum is σ = 1981209078. Its totient is φ = 1981209076.

The previous prime is 1981209073. The next prime is 1981209079. The reversal of 1981209077 is 7709021891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1727316721 + 253892356 = 41561^2 + 15934^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981209077 - 2² = 1981209073 is a prime.

Together with 1981209079, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1981209073) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990604538 + 990604539.

It is an arithmetic number, because the mean of its divisors is an integer number (990604539).

Almost surely, 2^1981209077 is an apocalyptic number.

It is an amenable number.

1981209077 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981209077 is an equidigital number, since it uses as much as digits as its factorization.

1981209077 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 63504, while the sum is 44.

The square root of 1981209077 is about 44510.7748416044. The cubic root of 1981209077 is about 1255.9627807290.

The spelling of 1981209077 in words is "one billion, nine hundred eighty-one million, two hundred nine thousand, seventy-seven".