78637981 has 2 divisors, whose sum is σ = 78637982. Its totient is φ = 78637980.

The previous prime is 78637963. The next prime is 78637991. The reversal of 78637981 is 18973687.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77352025 + 1285956 = 8795^2 + 1134^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78637981 is a prime.

It is a super-2 number, since 2×78637981² = 12367864111512722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78637901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39318990 + 39318991.

It is an arithmetic number, because the mean of its divisors is an integer number (39318991).

Almost surely, 2^78637981 is an apocalyptic number.

It is an amenable number.

78637981 is a deficient number, since it is larger than the sum of its proper divisors (1).

78637981 is an equidigital number, since it uses as much as digits as its factorization.

78637981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 508032, while the sum is 49.

The square root of 78637981 is about 8867.8058729316. The cubic root of 78637981 is about 428.4276103837.

The spelling of 78637981 in words is "seventy-eight million, six hundred thirty-seven thousand, nine hundred eighty-one".