1987391951 has 2 divisors, whose sum is σ = 1987391952. Its totient is φ = 1987391950.

The previous prime is 1987391947. The next prime is 1987391957. The reversal of 1987391951 is 1591937891.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1987391951 - 2² = 1987391947 is a prime.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 1987391893 and 1987391902.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1987391957) 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, 993695975 + 993695976.

It is an arithmetic number, because the mean of its divisors is an integer number (993695976).

Almost surely, 2^1987391951 is an apocalyptic number.

1987391951 is a deficient number, since it is larger than the sum of its proper divisors (1).

1987391951 is an equidigital number, since it uses as much as digits as its factorization.

1987391951 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 612360, while the sum is 53.

The square root of 1987391951 is about 44580.1744164376. The cubic root of 1987391951 is about 1257.2679425867.

The spelling of 1987391951 in words is "one billion, nine hundred eighty-seven million, three hundred ninety-one thousand, nine hundred fifty-one".