1987391947 has 2 divisors, whose sum is σ = 1987391948. Its totient is φ = 1987391946.

The previous prime is 1987391929. The next prime is 1987391951. The reversal of 1987391947 is 7491937891.

It is a strong prime.

It is an emirp because it is prime and its reverse (7491937891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1987391947 - 2²³ = 1979003339 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1987391891 and 1987391900.

It is not a weakly prime, because it can be changed into another prime (1987391957) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 993695973 + 993695974.

It is an arithmetic number, because the mean of its divisors is an integer number (993695974).

Almost surely, 2^1987391947 is an apocalyptic number.

1987391947 is a deficient number, since it is larger than the sum of its proper divisors (1).

1987391947 is an equidigital number, since it uses as much as digits as its factorization.

1987391947 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3429216, while the sum is 58.

The square root of 1987391947 is about 44580.1743715746. The cubic root of 1987391947 is about 1257.2679417432.

The spelling of 1987391947 in words is "one billion, nine hundred eighty-seven million, three hundred ninety-one thousand, nine hundred forty-seven".