78785981 has 2 divisors, whose sum is σ = 78785982. Its totient is φ = 78785980.

The previous prime is 78785947. The next prime is 78785983. The reversal of 78785981 is 18958787.

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., 73188025 + 5597956 = 8555^2 + 2366^2 .

It is an emirp because it is prime and its reverse (18958787) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78785981 is a prime.

It is a super-2 number, since 2×78785981² = 12414461604264722, which contains 22 as substring.

Together with 78785983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78785983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39392990 + 39392991.

It is an arithmetic number, because the mean of its divisors is an integer number (39392991).

Almost surely, 2^78785981 is an apocalyptic number.

78785981 is the 4745-th centered heptagonal number.

It is an amenable number.

78785981 is a deficient number, since it is larger than the sum of its proper divisors (1).

78785981 is an equidigital number, since it uses as much as digits as its factorization.

78785981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1128960, while the sum is 53.

The square root of 78785981 is about 8876.1467428158. The cubic root of 78785981 is about 428.6962148955.

It can be divided in two parts, 787 and 85981, that added together give a palindrome (86768).

The spelling of 78785981 in words is "seventy-eight million, seven hundred eighty-five thousand, nine hundred eighty-one".