78001681 has 4 divisors (see below), whose sum is σ = 78022692. Its totient is φ = 77980672.

The previous prime is 78001633. The next prime is 78001691. The reversal of 78001681 is 18610087.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18610087 = 17 ⋅1094711.

It can be written as a sum of positive squares in 2 ways, for example, as 46022656 + 31979025 = 6784^2 + 5655^2 .

It is a cyclic number.

It is not a de Polignac number, because 78001681 - 2¹¹ = 77999633 is a prime.

It is a super-2 number, since 2×78001681² = 12168524477651522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78001691) 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, 3280 + ... + 12913.

It is an arithmetic number, because the mean of its divisors is an integer number (19505673).

Almost surely, 2^78001681 is an apocalyptic number.

It is an amenable number.

78001681 is a deficient number, since it is larger than the sum of its proper divisors (21011).

78001681 is a wasteful number, since it uses less digits than its factorization.

78001681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21010.

The product of its (nonzero) digits is 2688, while the sum is 31.

The square root of 78001681 is about 8831.8560336998. The cubic root of 78001681 is about 427.2689375235.

The spelling of 78001681 in words is "seventy-eight million, one thousand, six hundred eighty-one".