71991797 has 4 divisors (see below), whose sum is σ = 72978060. Its totient is φ = 71005536.

The previous prime is 71991781. The next prime is 71991823. The reversal of 71991797 is 79719917.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 79719917 = 149 ⋅535033.

It can be written as a sum of positive squares in 2 ways, for example, as 14853316 + 57138481 = 3854^2 + 7559^2 .

It is a cyclic number.

It is not a de Polignac number, because 71991797 - 2⁴ = 71991781 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71991737) 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, 493022 + ... + 493167.

It is an arithmetic number, because the mean of its divisors is an integer number (18244515).

Almost surely, 2^71991797 is an apocalyptic number.

It is an amenable number.

71991797 is a deficient number, since it is larger than the sum of its proper divisors (986263).

71991797 is an equidigital number, since it uses as much as digits as its factorization.

71991797 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 986262.

The product of its digits is 250047, while the sum is 50.

The square root of 71991797 is about 8484.7979940597. The cubic root of 71991797 is about 416.0009650033. Note that the first 3 decimals are identical.

The spelling of 71991797 in words is "seventy-one million, nine hundred ninety-one thousand, seven hundred ninety-seven".