644651073 has 24 divisors (see below), whose sum is σ = 1021107360. Its totient is φ = 388661760.

The previous prime is 644651053. The next prime is 644651087. The reversal of 644651073 is 370156446.

It is a happy number.

644651073 is a `hidden beast` number, since 644 + 6 + 5 + 1 + 0 + 7 + 3 = 666.

It is not a de Polignac number, because 644651073 - 2⁶ = 644651009 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644651053) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2238 + ... + 35976.

It is an arithmetic number, because the mean of its divisors is an integer number (42546140).

Almost surely, 2^644651073 is an apocalyptic number.

It is an amenable number.

644651073 is a deficient number, since it is larger than the sum of its proper divisors (376456287).

644651073 is a wasteful number, since it uses less digits than its factorization.

644651073 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33949 (or 33946 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 36.

The square root of 644651073 is about 25389.9797754941. The cubic root of 644651073 is about 863.8564294943.

The spelling of 644651073 in words is "six hundred forty-four million, six hundred fifty-one thousand, seventy-three".