78406639 has 2 divisors, whose sum is σ = 78406640. Its totient is φ = 78406638.

The previous prime is 78406621. The next prime is 78406651. The reversal of 78406639 is 93660487.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 78406639 - 2⁷ = 78406511 is a prime.

It is a super-2 number, since 2×78406639² = 12295202078552642, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 78406595 and 78406604.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78406439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39203319 + 39203320.

It is an arithmetic number, because the mean of its divisors is an integer number (39203320).

Almost surely, 2^78406639 is an apocalyptic number.

78406639 is a deficient number, since it is larger than the sum of its proper divisors (1).

78406639 is an equidigital number, since it uses as much as digits as its factorization.

78406639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 217728, while the sum is 43.

The square root of 78406639 is about 8854.7523398455. The cubic root of 78406639 is about 428.0070729172.

The spelling of 78406639 in words is "seventy-eight million, four hundred six thousand, six hundred thirty-nine".