78081691 has 2 divisors, whose sum is σ = 78081692. Its totient is φ = 78081690.

The previous prime is 78081677. The next prime is 78081701. The reversal of 78081691 is 19618087.

It is a strong prime.

It is an emirp because it is prime and its reverse (19618087) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78081691 - 2²¹ = 75984539 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (78081631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39040845 + 39040846.

It is an arithmetic number, because the mean of its divisors is an integer number (39040846).

Almost surely, 2^78081691 is an apocalyptic number.

78081691 is a deficient number, since it is larger than the sum of its proper divisors (1).

78081691 is an equidigital number, since it uses as much as digits as its factorization.

78081691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24192, while the sum is 40.

The square root of 78081691 is about 8836.3844981983. The cubic root of 78081691 is about 427.4149775628.

The spelling of 78081691 in words is "seventy-eight million, eighty-one thousand, six hundred ninety-one".