644855892 has 12 divisors (see below), whose sum is σ = 1504663776. Its totient is φ = 214951960.

The previous prime is 644855863. The next prime is 644855921. The reversal of 644855892 is 298558446.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (644855863) and next prime (644855921).

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26868984 + ... + 26869007.

It is an arithmetic number, because the mean of its divisors is an integer number (125388648).

Almost surely, 2^644855892 is an apocalyptic number.

It is an amenable number.

644855892 is an abundant number, since it is smaller than the sum of its proper divisors (859807884).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644855892 is a wasteful number, since it uses less digits than its factorization.

644855892 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53737998 (or 53737996 counting only the distinct ones).

The product of its digits is 2764800, while the sum is 51.

The square root of 644855892 is about 25394.0129164337. The cubic root of 644855892 is about 863.9479081677.

The spelling of 644855892 in words is "six hundred forty-four million, eight hundred fifty-five thousand, eight hundred ninety-two".