644959161 has 144 divisors (see below), whose sum is σ = 1269224320. Its totient is φ = 307929600.

The previous prime is 644959121. The next prime is 644959163. The reversal of 644959161 is 161959446.

It is a happy number.

It is not a de Polignac number, because 644959161 - 2¹⁹ = 644434873 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (644959163) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 8835021 + ... + 8835093.

Almost surely, 2^644959161 is an apocalyptic number.

644959161 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

644959161 is a deficient number, since it is larger than the sum of its proper divisors (624265159).

644959161 is a wasteful number, since it uses less digits than its factorization.

644959161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188 (or 174 counting only the distinct ones).

The product of its digits is 233280, while the sum is 45.

The square root of 644959161 is about 25396.0461686460. The cubic root of 644959161 is about 863.9940240392.

It can be divided in two parts, 644 and 959161, that added together give a triangular number (959805 = T₁₃₈₅).

The spelling of 644959161 in words is "six hundred forty-four million, nine hundred fifty-nine thousand, one hundred sixty-one".