1981788157 has 2 divisors, whose sum is σ = 1981788158. Its totient is φ = 1981788156.

The previous prime is 1981788143. The next prime is 1981788161. The reversal of 1981788157 is 7518871891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1280279961 + 701508196 = 35781^2 + 26486^2 .

It is an emirp because it is prime and its reverse (7518871891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1981788157 - 2²⁷ = 1847570429 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1981788098 and 1981788107.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1981788197) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990894078 + 990894079.

It is an arithmetic number, because the mean of its divisors is an integer number (990894079).

Almost surely, 2^1981788157 is an apocalyptic number.

It is an amenable number.

1981788157 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981788157 is an equidigital number, since it uses as much as digits as its factorization.

1981788157 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1128960, while the sum is 55.

The square root of 1981788157 is about 44517.2793081518. The cubic root of 1981788157 is about 1256.0851356564.

The spelling of 1981788157 in words is "one billion, nine hundred eighty-one million, seven hundred eighty-eight thousand, one hundred fifty-seven".