78291209 has 2 divisors, whose sum is σ = 78291210. Its totient is φ = 78291208.

The previous prime is 78291193. The next prime is 78291247. The reversal of 78291209 is 90219287.

It is an a-pointer prime, because the next prime (78291247) can be obtained adding 78291209 to its sum of digits (38).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 48260809 + 30030400 = 6947^2 + 5480^2 .

It is an emirp because it is prime and its reverse (90219287) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78291209 - 2⁴ = 78291193 is a prime.

It is a super-2 number, since 2×78291209² = 12259026813363362, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (78291299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39145604 + 39145605.

It is an arithmetic number, because the mean of its divisors is an integer number (39145605).

Almost surely, 2^78291209 is an apocalyptic number.

It is an amenable number.

78291209 is a deficient number, since it is larger than the sum of its proper divisors (1).

78291209 is an equidigital number, since it uses as much as digits as its factorization.

78291209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 78291209 is about 8848.2319702865. The cubic root of 78291209 is about 427.7969328854.

The spelling of 78291209 in words is "seventy-eight million, two hundred ninety-one thousand, two hundred nine".