51172991 has 4 divisors (see below), whose sum is σ = 51197832. Its totient is φ = 51148152.

The previous prime is 51172987. The next prime is 51172997. The reversal of 51172991 is 19927115.

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 51172991 - 2² = 51172987 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 (51172997) 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, 9020 + ... + 13553.

It is an arithmetic number, because the mean of its divisors is an integer number (12799458).

Almost surely, 2^51172991 is an apocalyptic number.

51172991 is a deficient number, since it is larger than the sum of its proper divisors (24841).

51172991 is a wasteful number, since it uses less digits than its factorization.

51172991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24840.

The product of its digits is 5670, while the sum is 35.

The square root of 51172991 is about 7153.5299677851. The cubic root of 51172991 is about 371.2618011039.

The spelling of 51172991 in words is "fifty-one million, one hundred seventy-two thousand, nine hundred ninety-one".