644420505061 has 4 divisors (see below), whose sum is σ = 682327593612. Its totient is φ = 606513416512.

The previous prime is 644420505049. The next prime is 644420505073. The reversal of 644420505061 is 160505024446.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (644420505049) and next prime (644420505073).

It can be written as a sum of positive squares in 2 ways, for example, as 513846682561 + 130573822500 = 716831^2 + 361350^2 .

It is a cyclic number.

It is not a de Polignac number, because 644420505061 - 2²⁵ = 644386950629 is a prime.

It is a super-2 number, since 2×644420505061² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644420505061.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644420545061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18953544250 + ... + 18953544283.

It is an arithmetic number, because the mean of its divisors is an integer number (170581898403).

Almost surely, 2^644420505061 is an apocalyptic number.

It is an amenable number.

644420505061 is a deficient number, since it is larger than the sum of its proper divisors (37907088551).

644420505061 is a wasteful number, since it uses less digits than its factorization.

644420505061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37907088550.

The product of its (nonzero) digits is 115200, while the sum is 37.

The spelling of 644420505061 in words is "six hundred forty-four billion, four hundred twenty million, five hundred five thousand, sixty-one".