644181497 has 2 divisors, whose sum is σ = 644181498. Its totient is φ = 644181496.

The previous prime is 644181487. The next prime is 644181511. The reversal of 644181497 is 794181446.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 630461881 + 13719616 = 25109^2 + 3704^2 .

It is a cyclic number.

It is not a de Polignac number, because 644181497 - 2⁴ = 644181481 is a prime.

It is a super-3 number, since 3×644181497³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644181427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322090748 + 322090749.

It is an arithmetic number, because the mean of its divisors is an integer number (322090749).

Almost surely, 2^644181497 is an apocalyptic number.

It is an amenable number.

644181497 is a deficient number, since it is larger than the sum of its proper divisors (1).

644181497 is an equidigital number, since it uses as much as digits as its factorization.

644181497 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 44.

The square root of 644181497 is about 25380.7308208412. The cubic root of 644181497 is about 863.6466287731.

The spelling of 644181497 in words is "six hundred forty-four million, one hundred eighty-one thousand, four hundred ninety-seven".