644857971 has 16 divisors (see below), whose sum is σ = 888366336. Its totient is φ = 415822176.

The previous prime is 644857951. The next prime is 644857979. The reversal of 644857971 is 179758446.

It is not a de Polignac number, because 644857971 - 2¹¹ = 644855923 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644857979) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10980 + ... + 37553.

It is an arithmetic number, because the mean of its divisors is an integer number (55522896).

Almost surely, 2^644857971 is an apocalyptic number.

644857971 is a deficient number, since it is larger than the sum of its proper divisors (243508365).

644857971 is a wasteful number, since it uses less digits than its factorization.

644857971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48682.

The product of its digits is 1693440, while the sum is 51.

The square root of 644857971 is about 25394.0538512464. The cubic root of 644857971 is about 863.9488366158.

The spelling of 644857971 in words is "six hundred forty-four million, eight hundred fifty-seven thousand, nine hundred seventy-one".