78631661 has 2 divisors, whose sum is σ = 78631662. Its totient is φ = 78631660.

The previous prime is 78631639. The next prime is 78631667. The reversal of 78631661 is 16613687.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 54316900 + 24314761 = 7370^2 + 4931^2 .

It is an emirp because it is prime and its reverse (16613687) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78631661 - 2¹⁰ = 78630637 is a prime.

It is a super-2 number, since 2×78631661² = 12365876223237842, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78631667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39315830 + 39315831.

It is an arithmetic number, because the mean of its divisors is an integer number (39315831).

Almost surely, 2^78631661 is an apocalyptic number.

It is an amenable number.

78631661 is a deficient number, since it is larger than the sum of its proper divisors (1).

78631661 is an equidigital number, since it uses as much as digits as its factorization.

78631661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 38.

The square root of 78631661 is about 8867.4495205781. The cubic root of 78631661 is about 428.4161327449.

The spelling of 78631661 in words is "seventy-eight million, six hundred thirty-one thousand, six hundred sixty-one".