71899991 has 4 divisors (see below), whose sum is σ = 73843272. Its totient is φ = 69956712.

The previous prime is 71899973. The next prime is 71900051. The reversal of 71899991 is 19999817.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-71899991 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 (71899931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 971585 + ... + 971658.

It is an arithmetic number, because the mean of its divisors is an integer number (18460818).

Almost surely, 2^71899991 is an apocalyptic number.

71899991 is a deficient number, since it is larger than the sum of its proper divisors (1943281).

71899991 is a wasteful number, since it uses less digits than its factorization.

71899991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1943280.

The product of its digits is 367416, while the sum is 53.

The square root of 71899991 is about 8479.3862395813. The cubic root of 71899991 is about 415.8240576706.

The spelling of 71899991 in words is "seventy-one million, eight hundred ninety-nine thousand, nine hundred ninety-one".