1915981 has 2 divisors, whose sum is σ = 1915982. Its totient is φ = 1915980.

The previous prime is 1915961. The next prime is 1915993. The reversal of 1915981 is 1895191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1713481 + 202500 = 1309^2 + 450^2 .

It is an emirp because it is prime and its reverse (1895191) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1915981 - 2⁷ = 1915853 is a prime.

It is a super-2 number, since 2×1915981² = 7341966384722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1915931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 957990 + 957991.

It is an arithmetic number, because the mean of its divisors is an integer number (957991).

2^1915981 is an apocalyptic number.

It is an amenable number.

1915981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1915981 is an equidigital number, since it uses as much as digits as its factorization.

1915981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3240, while the sum is 34.

The square root of 1915981 is about 1384.1896546355. The cubic root of 1915981 is about 124.2025176619.

The spelling of 1915981 in words is "one million, nine hundred fifteen thousand, nine hundred eighty-one".