644005131065 has 16 divisors (see below), whose sum is σ = 812560470480. Its totient is φ = 489283710720.

The previous prime is 644005131017. The next prime is 644005131079. The reversal of 644005131065 is 560131500446.

It can be written as a sum of positive squares in 8 ways, for example, as 79912505344 + 564092625721 = 282688^2 + 751061^2 .

It is not a de Polignac number, because 644005131065 - 2¹⁸ = 644004868921 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36396194 + ... + 36413883.

It is an arithmetic number, because the mean of its divisors is an integer number (50785029405).

Almost surely, 2^644005131065 is an apocalyptic number.

It is an amenable number.

644005131065 is a deficient number, since it is larger than the sum of its proper divisors (168555339415).

644005131065 is a wasteful number, since it uses less digits than its factorization.

644005131065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72810172.

The product of its (nonzero) digits is 43200, while the sum is 35.

The spelling of 644005131065 in words is "six hundred forty-four billion, five million, one hundred thirty-one thousand, sixty-five".