51205581 has 32 divisors (see below), whose sum is σ = 91802880. Its totient is φ = 27537408.

The previous prime is 51205577. The next prime is 51205591. The reversal of 51205581 is 18550215.

It is not a de Polignac number, because 51205581 - 2² = 51205577 is a prime.

It is a super-2 number, since 2×51205581² = 5244023051095122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51205501) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4756 + ... + 11181.

It is an arithmetic number, because the mean of its divisors is an integer number (2868840).

Almost surely, 2^51205581 is an apocalyptic number.

51205581 is a gapful number since it is divisible by the number (51) formed by its first and last digit.

It is an amenable number.

51205581 is a deficient number, since it is larger than the sum of its proper divisors (40597299).

51205581 is a wasteful number, since it uses less digits than its factorization.

51205581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15970 (or 15964 counting only the distinct ones).

The product of its (nonzero) digits is 2000, while the sum is 27.

The square root of 51205581 is about 7155.8075016032. The cubic root of 51205581 is about 371.3405982339.

Adding to 51205581 its reverse (18550215), we get a palindrome (69755796).

It can be divided in two parts, 5120 and 5581, that added together give a palindrome (10701).

The spelling of 51205581 in words is "fifty-one million, two hundred five thousand, five hundred eighty-one".