78391949 has 2 divisors, whose sum is σ = 78391950. Its totient is φ = 78391948.

The previous prime is 78391927. The next prime is 78391979. The reversal of 78391949 is 94919387.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 66015625 + 12376324 = 8125^2 + 3518^2 .

It is a cyclic number.

It is not a de Polignac number, because 78391949 - 2²⁰ = 77343373 is a prime.

It is a super-2 number, since 2×78391949² = 12290595336037202, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 78391897 and 78391906.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78391979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39195974 + 39195975.

It is an arithmetic number, because the mean of its divisors is an integer number (39195975).

Almost surely, 2^78391949 is an apocalyptic number.

It is an amenable number.

78391949 is a deficient number, since it is larger than the sum of its proper divisors (1).

78391949 is an equidigital number, since it uses as much as digits as its factorization.

78391949 is an evil number, because the sum of its binary digits is even.

The product of its digits is 489888, while the sum is 50.

The square root of 78391949 is about 8853.9228029162. The cubic root of 78391949 is about 427.9803412667.

The spelling of 78391949 in words is "seventy-eight million, three hundred ninety-one thousand, nine hundred forty-nine".