78142781 has 4 divisors (see below), whose sum is σ = 78174492. Its totient is φ = 78111072.

The previous prime is 78142747. The next prime is 78142783. The reversal of 78142781 is 18724187.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18724187 = 1429 ⋅13103.

It can be written as a sum of positive squares in 2 ways, for example, as 22714756 + 55428025 = 4766^2 + 7445^2 .

It is a cyclic number.

It is not a de Polignac number, because 78142781 - 2¹⁸ = 77880637 is a prime.

It is a super-2 number, since 2×78142781² = 12212588444827922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78142783) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11816 + ... + 17201.

It is an arithmetic number, because the mean of its divisors is an integer number (19543623).

Almost surely, 2^78142781 is an apocalyptic number.

It is an amenable number.

78142781 is a deficient number, since it is larger than the sum of its proper divisors (31711).

78142781 is a wasteful number, since it uses less digits than its factorization.

78142781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31710.

The product of its digits is 25088, while the sum is 38.

The square root of 78142781 is about 8839.8405528607. The cubic root of 78142781 is about 427.5264162968.

The spelling of 78142781 in words is "seventy-eight million, one hundred forty-two thousand, seven hundred eighty-one".