51001661609 has 4 divisors (see below), whose sum is σ = 51002180100. Its totient is φ = 51001143120.

The previous prime is 51001661603. The next prime is 51001661617. The reversal of 51001661609 is 90616610015.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 6671622400 + 44330039209 = 81680^2 + 210547^2 .

It is a cyclic number.

It is not a de Polignac number, because 51001661609 - 2²⁴ = 50984884393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51001661603) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61334 + ... + 325215.

It is an arithmetic number, because the mean of its divisors is an integer number (12750545025).

Almost surely, 2^51001661609 is an apocalyptic number.

It is an amenable number.

51001661609 is a deficient number, since it is larger than the sum of its proper divisors (518491).

51001661609 is a wasteful number, since it uses less digits than its factorization.

51001661609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 518490.

The product of its (nonzero) digits is 9720, while the sum is 35.

The spelling of 51001661609 in words is "fifty-one billion, one million, six hundred sixty-one thousand, six hundred nine".