642809856 has 128 divisors (see below), whose sum is σ = 1849659840. Its totient is φ = 197394432.

The previous prime is 642809837. The next prime is 642809861. The reversal of 642809856 is 658908246.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1277701 + ... + 1278203.

Almost surely, 2^642809856 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 642809856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (924829920).

642809856 is an abundant number, since it is smaller than the sum of its proper divisors (1206849984).

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

642809856 is an equidigital number, since it uses as much as digits as its factorization.

642809856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 549 (or 521 counting only the distinct ones).

The product of its (nonzero) digits is 829440, while the sum is 48.

The square root of 642809856 is about 25353.6951153081. The cubic root of 642809856 is about 863.0332121522.

The spelling of 642809856 in words is "six hundred forty-two million, eight hundred nine thousand, eight hundred fifty-six".