51561661 has 4 divisors (see below), whose sum is σ = 51622272. Its totient is φ = 51501052.

The previous prime is 51561637. The next prime is 51561673. The reversal of 51561661 is 16616515.

51561661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51561661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51561061) 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 3 ways as a sum of consecutive naturals, for example, 29011 + ... + 30736.

It is an arithmetic number, because the mean of its divisors is an integer number (12905568).

Almost surely, 2^51561661 is an apocalyptic number.

It is an amenable number.

51561661 is a deficient number, since it is larger than the sum of its proper divisors (60611).

51561661 is an equidigital number, since it uses as much as digits as its factorization.

51561661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60610.

The product of its digits is 5400, while the sum is 31.

The square root of 51561661 is about 7180.6448874735. The cubic root of 51561661 is about 372.1993694673.

The spelling of 51561661 in words is "fifty-one million, five hundred sixty-one thousand, six hundred sixty-one".