1871981 has 2 divisors, whose sum is σ = 1871982. Its totient is φ = 1871980.

The previous prime is 1871957. The next prime is 1871983. The reversal of 1871981 is 1891781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1612900 + 259081 = 1270^2 + 509^2 .

It is a cyclic number.

It is not a de Polignac number, because 1871981 - 2⁶ = 1871917 is a prime.

It is a super-2 number, since 2×1871981² = 7008625728722, which contains 22 as substring.

Together with 1871983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1871983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 935990 + 935991.

It is an arithmetic number, because the mean of its divisors is an integer number (935991).

2^1871981 is an apocalyptic number.

It is an amenable number.

1871981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1871981 is an equidigital number, since it uses as much as digits as its factorization.

1871981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4032, while the sum is 35.

The square root of 1871981 is about 1368.2035667254. The cubic root of 1871981 is about 123.2443859929.

The spelling of 1871981 in words is "one million, eight hundred seventy-one thousand, nine hundred eighty-one".