644878998 has 24 divisors (see below), whose sum is σ = 1429733448. Its totient is φ = 209960352.

The previous prime is 644878967. The next prime is 644878999. The reversal of 644878998 is 899878446.

644878998 is a `hidden beast` number, since 64 + 487 + 8 + 9 + 98 = 666.

It is a super-2 number, since 2×644878998² = 831737844122968008, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644878999) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 415815 + ... + 417362.

It is an arithmetic number, because the mean of its divisors is an integer number (59572227).

Almost surely, 2^644878998 is an apocalyptic number.

644878998 is an abundant number, since it is smaller than the sum of its proper divisors (784854450).

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

644878998 is a wasteful number, since it uses less digits than its factorization.

644878998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 833228 (or 833225 counting only the distinct ones).

The product of its digits is 27869184, while the sum is 63.

The square root of 644878998 is about 25394.4678621152. The cubic root of 644878998 is about 863.9582268255.

The spelling of 644878998 in words is "six hundred forty-four million, eight hundred seventy-eight thousand, nine hundred ninety-eight".