645863778 has 48 divisors (see below), whose sum is σ = 1610831040. Its totient is φ = 183199968.

The previous prime is 645863767. The next prime is 645863797. The reversal of 645863778 is 877368546.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 925 + ... + 35952.

It is an arithmetic number, because the mean of its divisors is an integer number (33558980).

Almost surely, 2^645863778 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645863778, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (805415520).

645863778 is an abundant number, since it is smaller than the sum of its proper divisors (964967262).

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

645863778 is a wasteful number, since it uses less digits than its factorization.

645863778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37031 (or 37028 counting only the distinct ones).

The product of its digits is 6773760, while the sum is 54.

The square root of 645863778 is about 25413.8501215381. The cubic root of 645863778 is about 864.3977801209.

The spelling of 645863778 in words is "six hundred forty-five million, eight hundred sixty-three thousand, seven hundred seventy-eight".