1663681644 has 18 divisors (see below), whose sum is σ = 4205417580. Its totient is φ = 554560536.

The previous prime is 1663681637. The next prime is 1663681697. The reversal of 1663681644 is 4461863661.

1663681644 is a `hidden beast` number, since 1 + 6 + 636 + 8 + 1 + 6 + 4 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×1663681644² = 5535673225165085472, which contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 1663681644.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 23106654 + ... + 23106725.

It is an arithmetic number, because the mean of its divisors is an integer number (233634310).

Almost surely, 2^1663681644 is an apocalyptic number.

It is an amenable number.

1663681644 is an abundant number, since it is smaller than the sum of its proper divisors (2541735936).

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

1663681644 is a wasteful number, since it uses less digits than its factorization.

1663681644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46213389 (or 46213384 counting only the distinct ones).

The product of its digits is 497664, while the sum is 45.

The square root of 1663681644 is about 40788.2537503139. The cubic root of 1663681644 is about 1184.9228513573.

The spelling of 1663681644 in words is "one billion, six hundred sixty-three million, six hundred eighty-one thousand, six hundred forty-four".