78681509 has 2 divisors, whose sum is σ = 78681510. Its totient is φ = 78681508.

The previous prime is 78681479. The next prime is 78681523. The reversal of 78681509 is 90518687.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 76073284 + 2608225 = 8722^2 + 1615^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78681509 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 78681509.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78681539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39340754 + 39340755.

It is an arithmetic number, because the mean of its divisors is an integer number (39340755).

Almost surely, 2^78681509 is an apocalyptic number.

It is an amenable number.

78681509 is a deficient number, since it is larger than the sum of its proper divisors (1).

78681509 is an equidigital number, since it uses as much as digits as its factorization.

78681509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120960, while the sum is 44.

The square root of 78681509 is about 8870.2598045379. The cubic root of 78681509 is about 428.5066441069.

The spelling of 78681509 in words is "seventy-eight million, six hundred eighty-one thousand, five hundred nine".