644686860 has 48 divisors (see below), whose sum is σ = 1806336000. Its totient is φ = 171801024.

The previous prime is 644686841. The next prime is 644686873. The reversal of 644686860 is 68686446.

It is a super-2 number, since 2×644686860² = 831242294913319200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 123381 + ... + 128499.

It is an arithmetic number, because the mean of its divisors is an integer number (37632000).

Almost surely, 2^644686860 is an apocalyptic number.

644686860 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644686860 is an abundant number, since it is smaller than the sum of its proper divisors (1161649140).

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

644686860 is a wasteful number, since it uses less digits than its factorization.

644686860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7230 (or 7228 counting only the distinct ones).

The product of its (nonzero) digits is 1327104, while the sum is 48.

The square root of 644686860 is about 25390.6845122379. The cubic root of 644686860 is about 863.8724145025.

It can be divided in two parts, 644686 and 860, that added together give a palindrome (645546).

The spelling of 644686860 in words is "six hundred forty-four million, six hundred eighty-six thousand, eight hundred sixty".