78640439 has 2 divisors, whose sum is σ = 78640440. Its totient is φ = 78640438.

The previous prime is 78640433. The next prime is 78640481. The reversal of 78640439 is 93404687.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 78640439 - 2⁴ = 78640423 is a prime.

It is a super-2 number, since 2×78640439² = 12368637292225442, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 78640396 and 78640405.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78640433) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39320219 + 39320220.

It is an arithmetic number, because the mean of its divisors is an integer number (39320220).

Almost surely, 2^78640439 is an apocalyptic number.

78640439 is a deficient number, since it is larger than the sum of its proper divisors (1).

78640439 is an equidigital number, since it uses as much as digits as its factorization.

78640439 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 145152, while the sum is 41.

The square root of 78640439 is about 8867.9444630647. The cubic root of 78640439 is about 428.4320741474.

The spelling of 78640439 in words is "seventy-eight million, six hundred forty thousand, four hundred thirty-nine".