51481471991 has 4 divisors (see below), whose sum is σ = 51523567632. Its totient is φ = 51439376352.

The previous prime is 51481471961. The next prime is 51481472023. The reversal of 51481471991 is 19917418415.

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

It is a cyclic number.

It is not a de Polignac number, because 51481471991 - 2⁶ = 51481471927 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 (51481471961) 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, 21045986 + ... + 21048431.

It is an arithmetic number, because the mean of its divisors is an integer number (12880891908).

Almost surely, 2^51481471991 is an apocalyptic number.

51481471991 is a deficient number, since it is larger than the sum of its proper divisors (42095641).

51481471991 is a wasteful number, since it uses less digits than its factorization.

51481471991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42095640.

The product of its digits is 362880, while the sum is 50.

The spelling of 51481471991 in words is "fifty-one billion, four hundred eighty-one million, four hundred seventy-one thousand, nine hundred ninety-one".