51661661 has 4 divisors (see below), whose sum is σ = 51929532. Its totient is φ = 51393792.

The previous prime is 51661651. The next prime is 51661667. The reversal of 51661661 is 16616615.

51661661 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.

It can be written as a sum of positive squares in 2 ways, for example, as 33120025 + 18541636 = 5755^2 + 4306^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51661661 is a prime.

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 (51661667) 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, 133646 + ... + 134031.

It is an arithmetic number, because the mean of its divisors is an integer number (12982383).

Almost surely, 2^51661661 is an apocalyptic number.

It is an amenable number.

51661661 is a deficient number, since it is larger than the sum of its proper divisors (267871).

51661661 is a wasteful number, since it uses less digits than its factorization.

51661661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267870.

The product of its digits is 6480, while the sum is 32.

The square root of 51661661 is about 7187.6046774986. The cubic root of 51661661 is about 372.4398317304.

The spelling of 51661661 in words is "fifty-one million, six hundred sixty-one thousand, six hundred sixty-one".