78057781 has 2 divisors, whose sum is σ = 78057782. Its totient is φ = 78057780.

The previous prime is 78057751. The next prime is 78057787. The reversal of 78057781 is 18775087.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78039556 + 18225 = 8834^2 + 135^2 .

It is an emirp because it is prime and its reverse (18775087) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78057781 - 2⁹ = 78057269 is a prime.

It is a super-2 number, since 2×78057781² = 12186034349287922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78057787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39028890 + 39028891.

It is an arithmetic number, because the mean of its divisors is an integer number (39028891).

Almost surely, 2^78057781 is an apocalyptic number.

It is an amenable number.

78057781 is a deficient number, since it is larger than the sum of its proper divisors (1).

78057781 is an equidigital number, since it uses as much as digits as its factorization.

78057781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 109760, while the sum is 43.

The square root of 78057781 is about 8835.0314657051. The cubic root of 78057781 is about 427.3713457575.

The spelling of 78057781 in words is "seventy-eight million, fifty-seven thousand, seven hundred eighty-one".