51505581 has 4 divisors (see below), whose sum is σ = 68674112. Its totient is φ = 34337052.

The previous prime is 51505549. The next prime is 51505603. The reversal of 51505581 is 18550515.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 51505581 - 2⁵ = 51505549 is a prime.

It is a super-2 number, since 2×51505581² = 5305649748295122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51505501) 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, 8584261 + ... + 8584266.

It is an arithmetic number, because the mean of its divisors is an integer number (17168528).

Almost surely, 2^51505581 is an apocalyptic number.

It is an amenable number.

51505581 is a deficient number, since it is larger than the sum of its proper divisors (17168531).

51505581 is a wasteful number, since it uses less digits than its factorization.

51505581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17168530.

The product of its (nonzero) digits is 5000, while the sum is 30.

The square root of 51505581 is about 7176.7388833648. The cubic root of 51505581 is about 372.0643821392.

It can be divided in two parts, 5150 and 5581, that added together give a triangular number (10731 = T₁₄₆).

The spelling of 51505581 in words is "fifty-one million, five hundred five thousand, five hundred eighty-one".