1987981 has 2 divisors, whose sum is σ = 1987982. Its totient is φ = 1987980.

The previous prime is 1987969. The next prime is 1987987. The reversal of 1987981 is 1897891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1102500 + 885481 = 1050^2 + 941^2 .

It is a cyclic number.

It is not a de Polignac number, because 1987981 - 2¹⁷ = 1856909 is a prime.

It is a super-2 number, since 2×1987981² = 7904136912722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1987987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 993990 + 993991.

It is an arithmetic number, because the mean of its divisors is an integer number (993991).

2^1987981 is an apocalyptic number.

It is an amenable number.

1987981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1987981 is an equidigital number, since it uses as much as digits as its factorization.

1987981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 43.

The square root of 1987981 is about 1409.9578007870. The cubic root of 1987981 is about 125.7392145442.

The spelling of 1987981 in words is "one million, nine hundred eighty-seven thousand, nine hundred eighty-one".