644955956 has 6 divisors (see below), whose sum is σ = 1128672930. Its totient is φ = 322477976.

The previous prime is 644955947. The next prime is 644955959. The reversal of 644955956 is 659559446.

It can be written as a sum of positive squares in only one way, i.e., 630010000 + 14945956 = 25100^2 + 3866^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644955898 and 644955907.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644955959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80619491 + ... + 80619498.

It is an arithmetic number, because the mean of its divisors is an integer number (188112155).

Almost surely, 2^644955956 is an apocalyptic number.

It is an amenable number.

644955956 is a deficient number, since it is larger than the sum of its proper divisors (483716974).

644955956 is a wasteful number, since it uses less digits than its factorization.

644955956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161238993 (or 161238991 counting only the distinct ones).

The product of its digits is 5832000, while the sum is 53.

The square root of 644955956 is about 25395.9830681941. The cubic root of 644955956 is about 863.9925928863.

The spelling of 644955956 in words is "six hundred forty-four million, nine hundred fifty-five thousand, nine hundred fifty-six".