1987391993 has 2 divisors, whose sum is σ = 1987391994. Its totient is φ = 1987391992.

The previous prime is 1987391957. The next prime is 1987392013. The reversal of 1987391993 is 3991937891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1803870784 + 183521209 = 42472^2 + 13547^2 .

It is a cyclic number.

It is not a de Polignac number, because 1987391993 - 2⁶ = 1987391929 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1987301993) 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, 993695996 + 993695997.

It is an arithmetic number, because the mean of its divisors is an integer number (993695997).

Almost surely, 2^1987391993 is an apocalyptic number.

It is an amenable number.

1987391993 is a deficient number, since it is larger than the sum of its proper divisors (1).

1987391993 is an equidigital number, since it uses as much as digits as its factorization.

1987391993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3306744, while the sum is 59.

The square root of 1987391993 is about 44580.1748874990. The cubic root of 1987391993 is about 1257.2679514434.

The spelling of 1987391993 in words is "one billion, nine hundred eighty-seven million, three hundred ninety-one thousand, nine hundred ninety-three".