78637681 has 2 divisors, whose sum is σ = 78637682. Its totient is φ = 78637680.

The previous prime is 78637673. The next prime is 78637687. The reversal of 78637681 is 18673687.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 40704400 + 37933281 = 6380^2 + 6159^2 .

It is a cyclic number.

It is not a de Polignac number, because 78637681 - 2³ = 78637673 is a prime.

It is a super-2 number, since 2×78637681² = 12367769746115522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78637687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39318840 + 39318841.

It is an arithmetic number, because the mean of its divisors is an integer number (39318841).

Almost surely, 2^78637681 is an apocalyptic number.

It is an amenable number.

78637681 is a deficient number, since it is larger than the sum of its proper divisors (1).

78637681 is an equidigital number, since it uses as much as digits as its factorization.

78637681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 338688, while the sum is 46.

The square root of 78637681 is about 8867.7889577955. The cubic root of 78637681 is about 428.4270655730.

The spelling of 78637681 in words is "seventy-eight million, six hundred thirty-seven thousand, six hundred eighty-one".