644420505145 has 16 divisors (see below), whose sum is σ = 775201165200. Its totient is φ = 514272374784.

The previous prime is 644420505139. The next prime is 644420505149. The reversal of 644420505145 is 541505024446.

It can be written as a sum of positive squares in 8 ways, for example, as 408157432384 + 236263072761 = 638872^2 + 486069^2 .

It is a cyclic number.

It is not a de Polignac number, because 644420505145 - 2²¹ = 644418407993 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644420505098 and 644420505107.

It is not an unprimeable number, because it can be changed into a prime (644420505149) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19141267 + ... + 19174903.

It is an arithmetic number, because the mean of its divisors is an integer number (48450072825).

Almost surely, 2^644420505145 is an apocalyptic number.

It is an amenable number.

644420505145 is a deficient number, since it is larger than the sum of its proper divisors (130780660055).

644420505145 is a wasteful number, since it uses less digits than its factorization.

644420505145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42924.

The product of its (nonzero) digits is 384000, while the sum is 40.

The spelling of 644420505145 in words is "six hundred forty-four billion, four hundred twenty million, five hundred five thousand, one hundred forty-five".