78009317861 has 2 divisors, whose sum is σ = 78009317862. Its totient is φ = 78009317860.

The previous prime is 78009317831. The next prime is 78009317909. The reversal of 78009317861 is 16871390087.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 49119856900 + 28889460961 = 221630^2 + 169969^2 .

It is a cyclic number.

It is not a de Polignac number, because 78009317861 - 2⁶ = 78009317797 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78009317831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39004658930 + 39004658931.

It is an arithmetic number, because the mean of its divisors is an integer number (39004658931).

Almost surely, 2^78009317861 is an apocalyptic number.

It is an amenable number.

78009317861 is a deficient number, since it is larger than the sum of its proper divisors (1).

78009317861 is an equidigital number, since it uses as much as digits as its factorization.

78009317861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 508032, while the sum is 50.

The spelling of 78009317861 in words is "seventy-eight billion, nine million, three hundred seventeen thousand, eight hundred sixty-one".