644667081 has 8 divisors (see below), whose sum is σ = 910118304. Its totient is φ = 404496960.

The previous prime is 644667077. The next prime is 644667193. The reversal of 644667081 is 180766446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 644667081 - 2² = 644667077 is a prime.

It is a super-2 number, since 2×644667081² = 831191290650121122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644667011) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6320215 + ... + 6320316.

It is an arithmetic number, because the mean of its divisors is an integer number (113764788).

Almost surely, 2^644667081 is an apocalyptic number.

It is an amenable number.

644667081 is a deficient number, since it is larger than the sum of its proper divisors (265451223).

644667081 is a wasteful number, since it uses less digits than its factorization.

644667081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12640551.

The product of its (nonzero) digits is 193536, while the sum is 42.

The square root of 644667081 is about 25390.2950160096. The cubic root of 644667081 is about 863.8635798737.

The spelling of 644667081 in words is "six hundred forty-four million, six hundred sixty-seven thousand, eighty-one".