51131391 has 4 divisors (see below), whose sum is σ = 68175192. Its totient is φ = 34087592.

The previous prime is 51131389. The next prime is 51131411. The reversal of 51131391 is 19313115.

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 51131391 - 2¹ = 51131389 is a prime.

It is a super-2 number, since 2×51131391² = 5228838291189762, which contains 22 as substring.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51133391) 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, 8521896 + ... + 8521901.

It is an arithmetic number, because the mean of its divisors is an integer number (17043798).

Almost surely, 2^51131391 is an apocalyptic number.

51131391 is a deficient number, since it is larger than the sum of its proper divisors (17043801).

51131391 is a wasteful number, since it uses less digits than its factorization.

51131391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17043800.

The product of its digits is 405, while the sum is 24.

The square root of 51131391 is about 7150.6217212212. The cubic root of 51131391 is about 371.1611706893.

The spelling of 51131391 in words is "fifty-one million, one hundred thirty-one thousand, three hundred ninety-one".