644150561 has 2 divisors, whose sum is σ = 644150562. Its totient is φ = 644150560.

The previous prime is 644150539. The next prime is 644150569. The reversal of 644150561 is 165051446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 360430225 + 283720336 = 18985^2 + 16844^2 .

It is a cyclic number.

It is not a de Polignac number, because 644150561 - 2⁶ = 644150497 is a prime.

It is a super-2 number, since 2×644150561² = 829859890473229442, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (644150569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322075280 + 322075281.

It is an arithmetic number, because the mean of its divisors is an integer number (322075281).

Almost surely, 2^644150561 is an apocalyptic number.

It is an amenable number.

644150561 is a deficient number, since it is larger than the sum of its proper divisors (1).

644150561 is an equidigital number, since it uses as much as digits as its factorization.

644150561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14400, while the sum is 32.

The square root of 644150561 is about 25380.1213748083. The cubic root of 644150561 is about 863.6328033736.

The spelling of 644150561 in words is "six hundred forty-four million, one hundred fifty thousand, five hundred sixty-one".