1645661664 has 48 divisors (see below), whose sum is σ = 4799849040. Its totient is φ = 548553600.

The previous prime is 1645661651. The next prime is 1645661669. The reversal of 1645661664 is 4661665461.

It is a happy number.

1645661664 is a `hidden beast` number, since 16 + 4 + 566 + 16 + 64 = 666.

It is a tau number, because it is divible by the number of its divisors (48).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1645661669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 951487 + ... + 953214.

It is an arithmetic number, because the mean of its divisors is an integer number (99996855).

Almost surely, 2^1645661664 is an apocalyptic number.

It is an amenable number.

1645661664 is an abundant number, since it is smaller than the sum of its proper divisors (3154187376).

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

1645661664 is a wasteful number, since it uses less digits than its factorization.

1645661664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1904720 (or 1904706 counting only the distinct ones).

The product of its digits is 622080, while the sum is 45.

The square root of 1645661664 is about 40566.7556504091. The cubic root of 1645661664 is about 1180.6291923597.

The spelling of 1645661664 in words is "one billion, six hundred forty-five million, six hundred sixty-one thousand, six hundred sixty-four".