1321981 has 2 divisors, whose sum is σ = 1321982. Its totient is φ = 1321980.

The previous prime is 1321961. The next prime is 1321997. The reversal of 1321981 is 1891231.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 783225 + 538756 = 885^2 + 734^2 .

It is a cyclic number.

It is not a de Polignac number, because 1321981 - 2¹¹ = 1319933 is a prime.

It is a super-2 number, since 2×1321981² = 3495267528722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1321951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 660990 + 660991.

It is an arithmetic number, because the mean of its divisors is an integer number (660991).

2^1321981 is an apocalyptic number.

It is an amenable number.

1321981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1321981 is an equidigital number, since it uses as much as digits as its factorization.

1321981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432, while the sum is 25.

The square root of 1321981 is about 1149.7743256831. The cubic root of 1321981 is about 109.7509793863.

The spelling of 1321981 in words is "one million, three hundred twenty-one thousand, nine hundred eighty-one".