15981209 has 2 divisors, whose sum is σ = 15981210. Its totient is φ = 15981208.

The previous prime is 15981197. The next prime is 15981211. The reversal of 15981209 is 90218951.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12759184 + 3222025 = 3572^2 + 1795^2 .

It is a cyclic number.

It is not a de Polignac number, because 15981209 - 2⁴ = 15981193 is a prime.

It is a super-2 number, since 2×15981209² = 510798082203362, which contains 22 as substring.

Together with 15981211, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (15981239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7990604 + 7990605.

It is an arithmetic number, because the mean of its divisors is an integer number (7990605).

Almost surely, 2^15981209 is an apocalyptic number.

It is an amenable number.

15981209 is a deficient number, since it is larger than the sum of its proper divisors (1).

15981209 is an equidigital number, since it uses as much as digits as its factorization.

15981209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6480, while the sum is 35.

The square root of 15981209 is about 3997.6504349430. The cubic root of 15981209 is about 251.8855247671.

The spelling of 15981209 in words is "fifteen million, nine hundred eighty-one thousand, two hundred nine".