644777538 has 16 divisors (see below), whose sum is σ = 1345622976. Its totient is φ = 205581200.

The previous prime is 644777533. The next prime is 644777569. The reversal of 644777538 is 835777446.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (644777531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2336013 + ... + 2336288.

It is an arithmetic number, because the mean of its divisors is an integer number (84101436).

Almost surely, 2^644777538 is an apocalyptic number.

644777538 is an abundant number, since it is smaller than the sum of its proper divisors (700845438).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644777538 is a wasteful number, since it uses less digits than its factorization.

644777538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4672329.

The product of its digits is 3951360, while the sum is 51.

The square root of 644777538 is about 25392.4701043439. The cubic root of 644777538 is about 863.9129150696.

The spelling of 644777538 in words is "six hundred forty-four million, seven hundred seventy-seven thousand, five hundred thirty-eight".