78399437981 has 2 divisors, whose sum is σ = 78399437982. Its totient is φ = 78399437980.

The previous prime is 78399437953. The next prime is 78399437983. The reversal of 78399437981 is 18973499387.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74722956025 + 3676481956 = 273355^2 + 60634^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78399437981 is a prime.

It is a super-2 number, since 2×78399437981² (a number of 23 digits) contains 22 as substring.

Together with 78399437983, 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 (78399437983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39199718990 + 39199718991.

It is an arithmetic number, because the mean of its divisors is an integer number (39199718991).

Almost surely, 2^78399437981 is an apocalyptic number.

It is an amenable number.

78399437981 is a deficient number, since it is larger than the sum of its proper divisors (1).

78399437981 is an equidigital number, since it uses as much as digits as its factorization.

78399437981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 82301184, while the sum is 68.

The spelling of 78399437981 in words is "seventy-eight billion, three hundred ninety-nine million, four hundred thirty-seven thousand, nine hundred eighty-one".