1209389981 has 2 divisors, whose sum is σ = 1209389982. Its totient is φ = 1209389980.

The previous prime is 1209389971. The next prime is 1209390019. The reversal of 1209389981 is 1899839021.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1139400025 + 69989956 = 33755^2 + 8366^2 .

It is an emirp because it is prime and its reverse (1899839021) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1209389981 - 2¹⁸ = 1209127837 is a prime.

It is a super-2 number, since 2×1209389981² = 2925248252286360722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1209389941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 604694990 + 604694991.

It is an arithmetic number, because the mean of its divisors is an integer number (604694991).

Almost surely, 2^1209389981 is an apocalyptic number.

It is an amenable number.

1209389981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1209389981 is an equidigital number, since it uses as much as digits as its factorization.

1209389981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 279936, while the sum is 50.

The square root of 1209389981 is about 34776.2847498119. The cubic root of 1209389981 is about 1065.4231329430.

The spelling of 1209389981 in words is "one billion, two hundred nine million, three hundred eighty-nine thousand, nine hundred eighty-one".