644700545 has 4 divisors (see below), whose sum is σ = 773640660. Its totient is φ = 515760432.

The previous prime is 644700527. The next prime is 644700559. The reversal of 644700545 is 545007446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 545007446 = 2 ⋅272503723.

It can be written as a sum of positive squares in 2 ways, for example, as 437311744 + 207388801 = 20912^2 + 14401^2 .

It is a cyclic number.

It is not a de Polignac number, because 644700545 - 2⁸ = 644700289 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64470050 + ... + 64470059.

It is an arithmetic number, because the mean of its divisors is an integer number (193410165).

Almost surely, 2^644700545 is an apocalyptic number.

It is an amenable number.

644700545 is a deficient number, since it is larger than the sum of its proper divisors (128940115).

644700545 is a wasteful number, since it uses less digits than its factorization.

644700545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128940114.

The product of its (nonzero) digits is 67200, while the sum is 35.

The square root of 644700545 is about 25390.9539994070. The cubic root of 644700545 is about 863.8785270361.

The spelling of 644700545 in words is "six hundred forty-four million, seven hundred thousand, five hundred forty-five".