1665640644 has 48 divisors (see below), whose sum is σ = 3913963200. Its totient is φ = 551305216.

The previous prime is 1665640619. The next prime is 1665640651. The reversal of 1665640644 is 4460465661.

It is a junction number, because it is equal to n+sod(n) for n = 1665640596 and 1665640605.

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, 1291552 + ... + 1292840.

It is an arithmetic number, because the mean of its divisors is an integer number (81540900).

Almost surely, 2^1665640644 is an apocalyptic number.

It is an amenable number.

1665640644 is an abundant number, since it is smaller than the sum of its proper divisors (2248322556).

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

1665640644 is a wasteful number, since it uses less digits than its factorization.

1665640644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1972 (or 1970 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 42.

The square root of 1665640644 is about 40812.2609518267. The cubic root of 1665640644 is about 1185.3877546771.

The spelling of 1665640644 in words is "one billion, six hundred sixty-five million, six hundred forty thousand, six hundred forty-four".