644718149 has 4 divisors (see below), whose sum is σ = 682642764. Its totient is φ = 606793536.

The previous prime is 644718143. The next prime is 644718161. The reversal of 644718149 is 941817446.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 941817446 = 2 ⋅470908723.

It can be written as a sum of positive squares in 2 ways, for example, as 496487524 + 148230625 = 22282^2 + 12175^2 .

It is a cyclic number.

It is not a de Polignac number, because 644718149 - 2⁴ = 644718133 is a prime.

It is a super-2 number, since 2×644718149² = 831322983299972402, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644718143) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18962282 + ... + 18962315.

It is an arithmetic number, because the mean of its divisors is an integer number (170660691).

Almost surely, 2^644718149 is an apocalyptic number.

It is an amenable number.

644718149 is a deficient number, since it is larger than the sum of its proper divisors (37924615).

644718149 is a wasteful number, since it uses less digits than its factorization.

644718149 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37924614.

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

The square root of 644718149 is about 25391.3006559333. The cubic root of 644718149 is about 863.8863899007.

The spelling of 644718149 in words is "six hundred forty-four million, seven hundred eighteen thousand, one hundred forty-nine".