644642126621545 has 16 divisors (see below), whose sum is σ = 882080448374160. Its totient is φ = 448040862664704.

The previous prime is 644642126621531. The next prime is 644642126621569. The reversal of 644642126621545 is 545126621246446.

It can be written as a sum of positive squares in 8 ways, for example, as 149854909842576 + 494787216778969 = 12241524^2 + 22243813^2 .

It is a cyclic number.

It is not a de Polignac number, because 644642126621545 - 2²⁹ = 644641589750633 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644642126621545.

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, 291693268860 + ... + 291693271069.

It is an arithmetic number, because the mean of its divisors is an integer number (55130028023385).

Almost surely, 2^{644642126621545} is an apocalyptic number.

644642126621545 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

644642126621545 is a deficient number, since it is larger than the sum of its proper divisors (237438321752615).

644642126621545 is a wasteful number, since it uses less digits than its factorization.

644642126621545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 583386539964.

The product of its digits is 66355200, while the sum is 58.

The spelling of 644642126621545 in words is "six hundred forty-four trillion, six hundred forty-two billion, one hundred twenty-six million, six hundred twenty-one thousand, five hundred forty-five".