644561077 has 2 divisors, whose sum is σ = 644561078. Its totient is φ = 644561076.

The previous prime is 644561059. The next prime is 644561101. The reversal of 644561077 is 770165446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 642673201 + 1887876 = 25351^2 + 1374^2 .

It is a cyclic number.

It is not a de Polignac number, because 644561077 - 2⁷ = 644560949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644561677) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322280538 + 322280539.

It is an arithmetic number, because the mean of its divisors is an integer number (322280539).

Almost surely, 2^644561077 is an apocalyptic number.

It is an amenable number.

644561077 is a deficient number, since it is larger than the sum of its proper divisors (1).

644561077 is an equidigital number, since it uses as much as digits as its factorization.

644561077 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 141120, while the sum is 40.

The square root of 644561077 is about 25388.2074396756. The cubic root of 644561077 is about 863.8162282937.

The spelling of 644561077 in words is "six hundred forty-four million, five hundred sixty-one thousand, seventy-seven".