51561581 has 2 divisors, whose sum is σ = 51561582. Its totient is φ = 51561580.

The previous prime is 51561569. The next prime is 51561583. The reversal of 51561581 is 18516515.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 41538025 + 10023556 = 6445^2 + 3166^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51561581 is a prime.

It is a super-2 number, since 2×51561581² = 5317193270439122, which contains 22 as substring.

Together with 51561583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51561583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25780790 + 25780791.

It is an arithmetic number, because the mean of its divisors is an integer number (25780791).

Almost surely, 2^51561581 is an apocalyptic number.

It is an amenable number.

51561581 is a deficient number, since it is larger than the sum of its proper divisors (1).

51561581 is an equidigital number, since it uses as much as digits as its factorization.

51561581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6000, while the sum is 32.

The square root of 51561581 is about 7180.6393169411. The cubic root of 51561581 is about 372.1991769731.

The spelling of 51561581 in words is "fifty-one million, five hundred sixty-one thousand, five hundred eighty-one".