78951781 has 2 divisors, whose sum is σ = 78951782. Its totient is φ = 78951780.

The previous prime is 78951779. The next prime is 78951793. The reversal of 78951781 is 18715987.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 74666881 + 4284900 = 8641^2 + 2070^2 .

It is an emirp because it is prime and its reverse (18715987) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78951781 - 2¹ = 78951779 is a prime.

It is a super-2 number, since 2×78951781² = 12466767446143922, which contains 22 as substring.

Together with 78951779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78951701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39475890 + 39475891.

It is an arithmetic number, because the mean of its divisors is an integer number (39475891).

Almost surely, 2^78951781 is an apocalyptic number.

It is an amenable number.

78951781 is a deficient number, since it is larger than the sum of its proper divisors (1).

78951781 is an equidigital number, since it uses as much as digits as its factorization.

78951781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141120, while the sum is 46.

The square root of 78951781 is about 8885.4814726046. The cubic root of 78951781 is about 428.9967253424.

The spelling of 78951781 in words is "seventy-eight million, nine hundred fifty-one thousand, seven hundred eighty-one".