78640039 has 2 divisors, whose sum is σ = 78640040. Its totient is φ = 78640038.

The previous prime is 78640021. The next prime is 78640049. The reversal of 78640039 is 93004687.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 78640039 - 2⁵ = 78640007 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78640019) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39320019 + 39320020.

It is an arithmetic number, because the mean of its divisors is an integer number (39320020).

Almost surely, 2^78640039 is an apocalyptic number.

78640039 is a deficient number, since it is larger than the sum of its proper divisors (1).

78640039 is an equidigital number, since it uses as much as digits as its factorization.

78640039 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36288, while the sum is 37.

The square root of 78640039 is about 8867.9219098952. The cubic root of 78640039 is about 428.4313477479.

The spelling of 78640039 in words is "seventy-eight million, six hundred forty thousand, thirty-nine".