78240661 has 2 divisors, whose sum is σ = 78240662. Its totient is φ = 78240660.

The previous prime is 78240619. The next prime is 78240677. The reversal of 78240661 is 16604287.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 39614436 + 38626225 = 6294^2 + 6215^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78240661 is a prime.

It is a super-3 number, since 3×78240661³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78240601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39120330 + 39120331.

It is an arithmetic number, because the mean of its divisors is an integer number (39120331).

Almost surely, 2^78240661 is an apocalyptic number.

It is an amenable number.

78240661 is a deficient number, since it is larger than the sum of its proper divisors (1).

78240661 is an equidigital number, since it uses as much as digits as its factorization.

78240661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16128, while the sum is 34.

The square root of 78240661 is about 8845.3751192360. The cubic root of 78240661 is about 427.7048453439.

The spelling of 78240661 in words is "seventy-eight million, two hundred forty thousand, six hundred sixty-one".