51561565520 has 40 divisors (see below), whose sum is σ = 120941551656. Its totient is φ = 20442103808.

The previous prime is 51561565511. The next prime is 51561565529. The reversal of 51561565520 is 2556516515.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (51561565511) and next prime (51561565529).

It can be written as a sum of positive squares in 4 ways, for example, as 474716944 + 51086848576 = 21788^2 + 226024^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51561565529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2842817 + ... + 2860896.

Almost surely, 2^51561565520 is an apocalyptic number.

It is an amenable number.

51561565520 is an abundant number, since it is smaller than the sum of its proper divisors (69379986136).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

51561565520 is a wasteful number, since it uses less digits than its factorization.

51561565520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5703839 (or 5703833 counting only the distinct ones).

The product of its (nonzero) digits is 225000, while the sum is 41.

The spelling of 51561565520 in words is "fifty-one billion, five hundred sixty-one million, five hundred sixty-five thousand, five hundred twenty".