1987391957 has 2 divisors, whose sum is σ = 1987391958. Its totient is φ = 1987391956.

The previous prime is 1987391951. The next prime is 1987391993. The reversal of 1987391957 is 7591937891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1369074001 + 618317956 = 37001^2 + 24866^2 .

It is an emirp because it is prime and its reverse (7591937891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1987391957 - 2¹² = 1987387861 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1987391896 and 1987391905.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1987391951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 993695978 + 993695979.

It is an arithmetic number, because the mean of its divisors is an integer number (993695979).

Almost surely, 2^1987391957 is an apocalyptic number.

It is an amenable number.

1987391957 is a deficient number, since it is larger than the sum of its proper divisors (1).

1987391957 is an equidigital number, since it uses as much as digits as its factorization.

1987391957 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4286520, while the sum is 59.

The square root of 1987391957 is about 44580.1744837321. The cubic root of 1987391957 is about 1257.2679438519.

The spelling of 1987391957 in words is "one billion, nine hundred eighty-seven million, three hundred ninety-one thousand, nine hundred fifty-seven".