71778121 has 4 divisors (see below), whose sum is σ = 71822212. Its totient is φ = 71734032.

The previous prime is 71778079. The next prime is 71778127. The reversal of 71778121 is 12187717.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12187717 = 557 ⋅21881.

It can be written as a sum of positive squares in 2 ways, for example, as 35236096 + 36542025 = 5936^2 + 6045^2 .

It is a cyclic number.

It is not a de Polignac number, because 71778121 - 2²¹ = 69680969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (71778127) 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, 19506 + ... + 22891.

It is an arithmetic number, because the mean of its divisors is an integer number (17955553).

Almost surely, 2^71778121 is an apocalyptic number.

It is an amenable number.

71778121 is a deficient number, since it is larger than the sum of its proper divisors (44091).

71778121 is a wasteful number, since it uses less digits than its factorization.

71778121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44090.

The product of its digits is 5488, while the sum is 34.

The square root of 71778121 is about 8472.1969405816. The cubic root of 71778121 is about 415.5889851470.

The spelling of 71778121 in words is "seventy-one million, seven hundred seventy-eight thousand, one hundred twenty-one".