1909981 has 2 divisors, whose sum is σ = 1909982. Its totient is φ = 1909980.

The previous prime is 1909951. The next prime is 1909987. The reversal of 1909981 is 1899091.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1585081 + 324900 = 1259^2 + 570^2 .

It is a cyclic number.

It is not a de Polignac number, because 1909981 - 2⁵ = 1909949 is a prime.

It is a super-2 number, since 2×1909981² = 7296054840722, which contains 22 as substring.

1909981 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1909981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1909987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 954990 + 954991.

It is an arithmetic number, because the mean of its divisors is an integer number (954991).

2^1909981 is an apocalyptic number.

It is an amenable number.

1909981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1909981 is an equidigital number, since it uses as much as digits as its factorization.

1909981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 37.

The square root of 1909981 is about 1382.0206221327. The cubic root of 1909981 is about 124.0727330840.

The spelling of 1909981 in words is "one million, nine hundred nine thousand, nine hundred eighty-one".