78217681 has 4 divisors (see below), whose sum is σ = 80740864. Its totient is φ = 75694500.

The previous prime is 78217679. The next prime is 78217691. The reversal of 78217681 is 18671287.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18671287 = 17 ⋅1098311.

It is a cyclic number.

It is not a de Polignac number, because 78217681 - 2¹ = 78217679 is a prime.

It is a super-2 number, since 2×78217681² = 12236011242035522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (78217621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1261545 + ... + 1261606.

It is an arithmetic number, because the mean of its divisors is an integer number (20185216).

Almost surely, 2^78217681 is an apocalyptic number.

It is an amenable number.

78217681 is a deficient number, since it is larger than the sum of its proper divisors (2523183).

78217681 is a wasteful number, since it uses less digits than its factorization.

78217681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2523182.

The product of its digits is 37632, while the sum is 40.

The square root of 78217681 is about 8844.0760399264. The cubic root of 78217681 is about 427.6629676312.

The spelling of 78217681 in words is "seventy-eight million, two hundred seventeen thousand, six hundred eighty-one".